I can't offer any advice that hasn't already been said, besides go with Nikon, but I'm a Nikon guy so my opinion is biased and it's honestly 6 in one hand and half a dozen in the other. Personal preference really, both are great choices.
I started taking my photography semi-seriously about 5 years ago when I picked up a Nikon D40x w/ 18-55 and 55-200mm lenses used for $400.00. My camera was outdated back then (made in 2007 I believe) so today it's definitely old, obsolete technology, but I'm still using it. I've sold the kit lenses and bought an 18-200mm lens for no other reason than I like to take a lot of pictures of the city when I go on vacation and it's easier to carry one do-it-all lens than 2 purpose built lenses. I also picked up a Nikon SB800 Speed Light to make an attempt at indoor photography (ceremonies, etc.) but haven't honestly gotten much use out of it. My bread and butter so-to-speak is automotive photography (car shows/meets/cruises, etc.)
All that being said, yes I am still rocking my original DSLR that is now 10 years old, but I am looking to upgrade to a D7100 this Christmas. At around $600 (body only) it seems like the best upgrade out there for me, and I have 100% outgrown the D40X IMO. I am no professional by any stretch, but I take photography as a serious hobby and I enjoy doing it. No professional training whatsoever, just read a bit online, watched some videos, and had lots of time to practice.
