I vote Slash... despite being bashed for it's high CG design, it usually keeps up with the more race oriented trucks very well and its design makes it more forgiving - leading to more consistent lap times, especially for beginners.
I really wanted a Blitz when I was picking out my first SCT and decided to go for the Slash. It's sooo durable and it's the only truck that's waterproof right out-of-the-box...
Another thing is parts availability.. The 2 very small hobby shops in my town stock mainly Traxxas parts and 3/4 of the trucks at the track are Slashes so much more peer support too..