Now for my counterargument. Also, like you said, Baraba vs Ultroid Zero leads to both falling, as once the D4 Ray is fired, it'll either kill Baraba, or kill Baraba and everything around them when it comes in contact with the Yapool Dimension. Either way, both fall out of comission here. Now onto the main event, Geed vs Orb. Like you said, Orb has more experience, but Geed is also a natural fighter meaning the combat should be roughly the same between the two. Now onto the forms.
Specium Zeperion vs Primitive.
I will say, that the Wrecking Burst is far stronger than the Sperion Beam. No doubt about that. Both beams can kill monsters, but only one can match up with Belial. But, while Geed has the more powerful Beam, Orb has more energy attacks, as well as being able to circle around and fire multiple Sperion Beams at the same time.
It's a close one, the fight between base forms. Geed has a good natural fighting instinct and a stronger beam, but Orb has the stronger physical and speed advantage here by taking energy from Tiga's Power and Sky types. Orb also has a cutting halo that he can catch and toss around with ease or even enhance to be bigger than himself, though Geed has a slash type energy attack as well as a powerful roar. But, Orb has a multipurpose Energy Shield in this form while Geed does not, a shield he once used to reflect a beam and also once used to push an enemy into space. Though both times were circumstantial, it's still a form of defense he can use to help protect him momentarily from the sheer power of the Wrecking Burst. I'd give this one to Orb barely in a base form fight for more utility in his abilities.
Burnmite vs Solid Burning
This one is troublesome, but also an interesting fight between power type forms. Geed's form has a good defensive coverage with his armored plating and his speed is kept due to the various vents on his body that release steam and fire. His power in this form comes from his usage of those vents to speed up his heavier, armored body to deal heavy damage. He has sluggers to use at his leisure as well as the ability to install it on parts of his body and fight like Kamen Rider Amazon to slash foes apart. As for energy abilities, he has the Strike Boost, a flaming beam attack that he can use at both range and up close to deal heavy damage to enemies. He also has the power to fire off a powerful chest beam called the Solar Burst, and has an Emerium Beam from his forehead beam lamp. Overall, Geed has a nice defense and speed form here to use and enhance his fighting potential.
Burnmite however, is all in on attack and fiery ability. His speed is lowered a bit, but the trade off in strength and power is immense. His newfound ability to harness fire allows him to fire off bursts of flaming energy in the form of the Stobium burst, a similar attack to Mebius's own finishing attack called the Mebium Burst. As for a normal beam, he has the Stobium beam, which is just a combination of Taro and Mebius's beams. Most likely, it isn't as strong as the strike boost, but it is still versatile as a normal beam attack. Also, while Solid Burning has good defense, Burnmite brings out Explosive Power in a literal form via the Stobium Dynamite. A powerful explosion capable of killing monsters in one move, as it is taken from both the Ultra Dynamite and the Mebium Dynamite. However, Orb can also utilize the Stobium Dynamite in the form of a kick as well, giving him a literal explosive kick. His melee is complemented by usually being engulfed in flames, meaning they will have a fiery hit to them. Another thing, which will give him an edge in the Power Form battle, is that Orb can absorb other flames into his hand and counter with the Stobium Counter, which is basically just a charged up fire punch. He could possibly absorb the flames given off by Solid Burning and from the Strike Boost, and then counter it with his own fiery spirit.
In this fight, I'd probably say the two are equal and counter each other well, but leaning more towards Geed in this case for the Armor.
Hurricane Slash vs Acro Smasher
Orb wins the fight of Speed forms. Acro Smasher takes heavily from Cosmos in which many of his attacks are more pacifistic and calming, pushing away monsters rather than destroying them. And while he does have Hikari's Sword, that's his only lethal energy attack. He also has the Geed Claw to use sure, but that's his only other killing weapon in this form. Meanwhile, here comes Orb with two sluggers and the Orb Slugger Lance. Both the Sluggers and the Lance function as both weapons and barriers for Orb, while the Lance also has a powerful beam attack, can reflect attacks back with its barrier, and can create a tornado.
As for a battle of speed, Orb has this one. Geed might have faster reflexes here, but Orb both has the far better speed feats, able to strike multiple times and leave after images at the same time, but also teleportation in this form.
Thunder Breaster vs Magnificent
Now for the hard one. The Super Forms that both debut at episode 12. Let's start with Thunder Breaster.
To start with, Thunder Breaster is strong, strong enough to lift and throw Maga-Orochi who weighs 80,000 tons and tear off Galactron's tail hair thing on his head. He's durable enough to walk through Maga-Orochi's beam, something none of his other forms did, and to withstand Galactron's firepower enough to grab hold of the hand floating around firing the beam at him. His ability to channel dark energy to power up his attacks was enough to overpower Galactron and keep it pinned down to tear it apart. Now for Beams. His Zettcium Beam was powerful enough to destroy Maga-Orochi while his other forms couldn't. His Light Ring attack was sharp enough to cut off Maga-Orochi's tail, and also takes the form of his energy shield which took a hit from Magata no Orochi's Perforation beam and let him just wade through it. He also just walked through and knocked aside and wade through all the energy attacks of Magata No Orochi but the powered-up Maga Thunderclap in this form as well before he got bit and had his energy drained. His Energy Slicer was sharp enough to cut through Magata no Orochi's tentacles. He also has a Rotating Lariat attack.
Now for Magnificent. This one is also very durable. He was able to withstand the attacks of Pedanium Zetton pretty easily. The Big Bustaway was able to break through the energy shield formed by Pedanium Zetton and destroy it. His shield withstood attacks from Pedanium Zetton easily as well, and like Thunder Breaster, he was easily able to handle the attacks from a stronger opponent that beat his other forms. His horn lightning was able to knock back Pedanium Zetton, plus he's got large energy shurikens at his disposal. Also like Thunder Breaster, he can infuse his attacks with energy to make them stronger in the form of the Mega Bomber Punch and Dynamite which is a double punch that was also able to push back Pedanium Zetton. He can also swing his arm to send small energy blade circles out from the slicers on them. And while brief, he was able to keep up with and toss Chimeraberus in Magnificent. Plus I'm not sure if I can count his use of Magnificent against Belial Atrocious as he was also fighting alongside all his other forms there as well while Orb went solo and lost before his evil buddy Jugglus Juggler hopped in for that final battle.
Comparing the two is hard, but I'm giving it to Orb in this case. Orb's strength is far better than Magnificent, as while Geed was able to swing and toss Chimeraberus, Orb lifted up and threw the heavier Maga-Orochi. He also has better Durability feats, able to withstand the attacks of the stronger Magata No Orochi, while still being knocked around yes, but he was still able to get close enough to fight back and deflect a majority of its attacks. All this, while having less armor than Magnificent. That armor is going to slow Geed down while Orb will still have his better speed and maneuverability while still having similar levels of durability here. The light ring is going to hurt if it hits Geed, while likewise, Geed's Electric Horn will probably knock around Orb. Both have impressive energy shields.
And yes, each form doesn't have to fight against each other like so, but comparing the two gives me a bit of an edge in this round. Each form can counter the other in certain ways such as having water to cool down Burnmite or Solid Burning or using their speed forms against the others base forms, etc. The only one that would be problematic is if Geed tried to calm down Thunder Breaster, as that would only give Orb more of a level head if he starts going berserk. Geed is more defensive-oriented in his forms, but Orb is more Power focused on his own forms.