If you want a 1/5 truggy look at the arrma kraton 8S. I'm pretty smitten with mine. It's pretty fast and handles really well.
As for the other 2 you mentioned then DBXLE is a buggy and the outkast is basically a monster truck so given the area you'll be running it in which one seems better for...
Not necessarily but it could. At the very least it should run cooler. Size matters to a degree but you can compensate in other ways too like cell count and gearing as TNT mentioned.