I have them both and in my experience, they look and play a lot different. The Golf Club uses DirectX 11, which allows HBS to use fur shaders in their game. Fur shaders are allowing them to create rough that has a 3D-ish depth and texture, among other things. Perfect Golf uses DirectX 9, which allows older machines to be able to run the game, but also ties the developers hands a bit. Once you get to the secondary rough in PG, they use generic Unity textures, and they look very unnatural and blocky.
PG's custom textures which comprise the tees, fairways, greens, and first cut of rough look fine from low angles, but even they take on a blocky (although a lot less blocky look than Unity's textures) when viewed from a high angle. If you have the reverse angle enabled, the camera will sometimes cut to an extremely zoomed closeup of the hole from like an 80 degree overhead angle and that green texture that looked pretty natural from the swing camera, suddenly looks like something out of the 90's!?
Where I think PG has an advantage over TGC is there's a larger variety of course objects available to the designer and the courses look more distinctive. You can't look at a PG course and identify it with any "theme" constraints. It also has more of an "impressionistic" art style, which has its pluses and minuses. In ways, it looks less 3D than The Golf Club, but lends itself to yielding better screen shots.
What's killing PG for me though is the lack of a real time swing interface. Neither option (-click or motion/mouse) is real time. You execute the swing through completion, then watch a "serviceable" golfer animation carry out what you've told it to do during the control sequence immediately thereafter. It makes the experience feel disjointed and out of phase to me. Perfect Parallel is working on a real time motion swing interface, and they say eventually, one that uses thumbstick controllers. Until they do, PG will be little more than a curiosity to me. I still think they've tied themselves down with DirectX 9 in terms of moving forward, but we'll see...