They both have their own pros and cons. Nitro has more of a learning curve because of all the break in and tuning involved. I was a complete newbie to r/c when I got the T-Maxx. Once you see a nitro truck run, you'll probably want it over electric, they're just plain cool! I like Traxxas because they have a great website with a lot of support and troublshooting, and they also have a good forum (Yep ANOTHER one for me to hang out at!) Make sure the hobby shop you buy from has some good guys working there. You will be in there ALL the time, and it helps alot when the people are friendly and know what they're doing.
Nitro Pros:
Usually faster than electric
Gas it and go, no batteries
Can run all day, again, no batts to charge
Plenty of hop-ups to make them faster
They sound cool, and are basically just like little cars!
Nitro Cons:
Engines can be tricky to tune
Gas is about $25 a gallon (but you can get about 60 tanks of gas out of them)
The engine will not last forever. The leaner you run them, the faster they go, but the faster they burn out.
Most of the large hobby stores have a few types of cars they will let you test out. You can get a feel for what you like. Also, as a newbie, get a RTR (Ready to Run) model, that's what the T and E Maxx's are.