Im giving it to the T-800, especially since the Xeno has nowhere to hide in an african grassland which is generally how they try to take out a target. That being said, the T-800 can take out the xeno quite easly at a distance. Hes probably going to take lots of damage from the acid bloodbath afterwards tho.
If it comes to close quarters, the T-800 is more than capable of handeling the Xeno. T-800s can lift within the low multi tonne range and typically only other Terminators can take them in CQC. Also, while the Xenos themselves have displayed impressive strengh dfeats such as denting steel doors and such, the Terminator's Hyper Alloy Combat Chassis was able to withstand nearly all forms of small arms fire (unlike xenos. Granted they where 10mm explosive rounds but they can be killed by small arms fire none the less). The T-800 can also survive being submerged in molten steel, shot numerous times with a grenade launcher, and finally survived a massive gasoline explosion. They are also moderatly resistant to plasma. The'yve displayed more impressive feats in the comics, but Im too lazy to look those up.
TK's resident expert on Fallout, Halo, Terminator, and Gears of War
"Our species is destined to rule Sera, the humans can no longer deny it..."