I'm a big Gehl fan, but even I'd pass on 2600. I didn't even recognize the model number when I read it. Had to Google it. That machine has got to be at least 25 years old or more. If it only has 800 hours, that's either 800 hours on a new engine or 800 hours total, which means seals are probably old and cracked, and when put into real service (<40 hours per year isn't
real service), I'd expect lots of things to start breaking. Engine, hydros, controls, etc. (In fact,
here's a 2600 made in 1978.)
I know little about the Case, but it looks like it's from the same era, and was put to similar use.
If you need a machine for tight spaces and you don't mind not being able to lift more than a wheelbarrow or two worth of material, and you don't fear the likelihood of having to do some non-minor repairs, then they might work out great. But if you need a daily runner and you need it to work hard for you, you might want to consider newer, more powerful models.
Our Gehl 6635 has 80 hp and has been up to the jobs I have for it about 95% of the time. The other 5% I wish I had the 7000 series.