I'm just strictly in it to play the games, so my collection is a random mishmash of US & JP releases. I will of course tend to prefer a US version so I can actually read the manual, but if the JP version is quite a bit cheaper then I might get it instead. And I'm mostly in it with this platform for the shmups, and a huge chunk of them are Japanese only, further making me not care about region.
But I am picky about condition and loose hucards. I don't care about spine cards and cardboard boxes, but other than that everything I buy has to have the game, original case, and manual.