Any of the baja series are great vehicles. Plenty of power, durable, and TONS of aftermarket support. The Losi Five-T is a great, durable, and popular truck as well. However, the Losi is underpowered from the factory. With the Losi it'd be best to mod the engine or put a bigger engine in it. All you need to do to the HPI is put a pipe on it and you'll be good for power, unless you're power crazy.
I have no experience with any of the "off" brand 1/5 scale RC's, but I've heard many bad and good things about them. You don't here much bad about the HPI's or Losi's...