I'm about 30 hours into ff8 so far so I can't completely compare, but so far I think ff7 is better. I'm enjoying ff8 and it's quite an engaging game, but it gives you too many options to improve yourself and I haven't had even a slightly hard battle so far. It could get harder though as I haven't finished it yet.
I am completely biased though, as ff7 was my first rpg and I only got ff8 a couple of weeks ago.