I have a yfz450 and primarily ride trails. It's got plenty of power as you probably know and it's very fun. One drawback is that it doesn't have reverse so in case you do get stuck trying to make your own trail or something, getting off and pulling it out of a problem gets old fast. However, it provides me with the thrill of trying to rip it around instead of getting off and pulling (which I'm sure you will master with a little practice).
Overall i see the yfz450 as more of a race bike and it will always piss all over anything out there, probably the raptor 700, but if you can manage without a reverse gear I'd go for the yfz cuz it's so much more fun to jump and do hill climbs with. It's lighter and feels very relaxed when crawling around on rocks and going through trails (mainly because my suspension is set fairly soft).
Personally, I see the raptor 700 as more a trail bike mainly because it has the reverse gear so you can probably get unstuck a bit easier. I'm not familiar with the ground clearance on the raptor so if your trails have a lot of stumps and rocks, you should look into that because the yfz450 doesn't have much clearance at all. Also maintenance is apparently a big issue with the yfz450 due to valve clearances, very picky jetting (unless you get the fuel injection). It's a high compression motor so stuff tends to get worn out and will need replacing eventually. People have said the raptor doesn't need much maintenance at all, just change the oil every now and then and you're good to go.
So if I were you, find specs on both quads and line them up, compare the numbers, watch some videos on youtube and take things like ground clearance, weight, reverse, overall look, power, and maintenance in mind. Also which one do you feel more comfortable sitting on. See what suits you best and your riding style. If you can take, them both for a test run as that will most likely be the deciding factor.
goodluck and let us know what you do