I prefer hourglass to wire clips, but my favorite clips are the barrel clips from the Pacific Salt / Delica 3. One screw instead of three, you can swap carry sides with any two coins, and they never come loose for me. Hourglass and wire clips with their small torx screws sometimes do.
Wire clips have the best ergonomics while using the knife, but hourglass / barrel clips have always felt stronger and more secure for me.
I'm more inclined to buy a small, light knife like a UKPK with a wire clip than I am a big, heavy folder like a Manix XL. I almost exclusively carry bigger knives though.
Neither type of clip is a deal breaker for me, I have used all of them, but if I could have my choice I would put Endura 3 style barrel clips on everything.
Though one more point in favor of hourglass clips is they offer four way mounting. I rarely ever utilize tip up, but it's good for the general market to offer options.
Can't say I've ever scratched a car with any clip. I find it pretty easy not to rub up against them.
Couldn't care less about deep carry, and in fact I prefer a bit sticking out above the clip. Especially when carrying IWB.