I generally prefer party RPGs though I normally will play them with no more than 4 characters if they're designed for 6-8.
One thing I don't like, though, is the "fixed party that levels equally but you can only choose two characters + protagonist" thing that Jade Empire/KotoR/DA/Avadon/etc do. The individual games can be good, of course, but I find that particular mechanic to be rather annoying. Not only can I not get rid of anyone regardless of how useless or irritating they are, but there's generally an "all of your sidekicks working together!" mission towards the end of the game that's very poorly balanced. I even prefer the weird NPC recruitment scheme that Wizardry 8 uses to that nonsense.
Solo RPGs can be truly excellent, but there's often a strong undercurrent of murderhobo in those games that somewhat bothers me. The only real exception to that is Morrowind due to how integrated you can become in Dunmer society.