It's useful to have some, you'll thank yourself if it comes down to it and you don't have to run out to the store because both parties assumed the other would provide. I wouldn't want to make a generalisation about whether guys tend to carry condoms or not; I'd assume they would, because they must know partners will generally want them to wear them?? but, who knows. *shrugs* My partner always brings his own, but I always take some too, just in case he forgets, or some break, or we want to do it more than once.

If you're in the UK you can get them for free from your GP, I'm not sure what Planned Parenthood or other non-UK based sexual health services offer but it's worth looking.

As for different brands etc. I would just go with the most standard kind. Buy a box, keep them on hand. Your partner might have a different type they prefer, in which case they'll probably have them already. It's always good to be taking an active role in your contraception though, whatever form it takes.