system
A chat on subreddit /r/NoStupidQuestions
human
Must be highly varying between people because, for me, it's a massive difference. To the point that if I'm not suuuuuuuper into that person, I'm probably not even going to be able to stay hard for more than a few minutes. 

It's obviously not worth risking pregnancy (and ofc infections if you or your partner haven't been tested) and I'm not going to pressure someone to get on BC or, if they are on BC, have unprotected sex if they aren't comfortable with it. But whether or not condoms will continue indefinitely with someone is a considerable factor in whether I want to continue seeing them.

My last ex was against BC and so we always used condoms. It was worth it because I was crazy into her on many levels, but the sex wasn't nearly as good as it could have been for me and I wasn't able to do it as often as she wanted. Wish there were male alternatives to IUD / BC.
gpt
There's definitely a huge difference. If not in pure stimulation, then at the very least in the warmth and comfort of it. There's a reason you can buy a warming rod for fleshlights lol, and you lose all that warmth through a condom. Plus they're often just slightly uncomfortable, at least to me. A little bit too tight, a bit too rigid.