I'm not so worried about bonuses right now, but I do care about how long withdrawals take. I've had some places hold on to my funds for days without any clear reason, even after verification. It's hard to plan my bankroll when I don't know how fast I can actually get my winnings back into my account.
A lot of people focus on flashy features but forget to test how payouts actually work. I've seen delays even when the site says it's "instant," so I always recommend starting with a small withdrawal. You'll quickly see if their stated timelines match reality or if you'll be left waiting for no reason.