I sure wouldn't buy him as a stallion. He has a number of conformation faults - and is coarse looking overall. As a gelding he might make a decent pleasure horse - but again, certainly has some faults, mainly involving his legs - which is never a good thing.
To address the post about a stallion not making a great trail horse... one of my BEST trail horses (ever) was a stallion. Just because they have testicles doesn't make them any "worse" at being a riding horse, provided they have been trained properly and the rider knows how to handle a stallion. The little guy I'm talking about was respectful, quiet, intelligent and brave - most people who came across us on the trail assumed he was a gelding. To assess their "ability" to make a good riding horse you'd need to meet them in person and see what sort of foundation there is to work with. In all honesty, if I had a pleasure stallion which was "difficult" he wouldn't be a stallion anymore. (A top level competition horse I might be less critical of, since many top level horses can be "difficult" - be they mares or geldings)