Never shot either, but,
Buffalo can accept hoyt F2 F3 or F4 formula limbs.
Obviously Excel is ILF. You will have more limb options with the Excel, and probably alot more limb options in a reasonable price range.
Buffalo is 60" with the short limbs, 62" with medium limbs, and if you fit long Formula limbs you can get 64".
Excel 21" riser makes a 62"(short) 64" (medium), or a 66" (long) bow.
What's your draw length? a long draw might do better with the Buffalo at a given bow length cause you'll have more limb and less riser.
If you wanna hunt form a blind with it, shorter is probably better ... might go Buffalo.
Personally I'd go Excel, for the price of a buffalo you can get an excel riser and two sets of blackmax carbon/wood limbs.
I don't if you're into rifles at all but my arguement for ILF is the same as for using common rifle calibers. If you're out on a trip away from your stomping grounds, would you rather have to find 30-06 ammo in a pinch or .30-338 magnum wildcat rounds? Same goes for ILF vs Formula. If it really came down to it, and you had to get limbs short notice, you're alot more likely to find some ILF limbs in the local shop than some formula limbs,