The slayer should go 50 or so I think. Its a revo with short arms and smaller tires. The main thing I dont like about the slayer is that they seem pretty unstable. Turns at speed make the slayer roll very easily.
I have owned both 1/8 buggies, and the jato. Id have a hard time telling you what i think is best. If you are going to be on the road a lot, then the jato is probably going to keep your interest better. If you will be in the yard very much, the buggy will be nicer, and for Jumps, the buggy will jump better and be more forgiving(tougher) hands down. The buggy will be much better on a track, but if you arent at the track, it wont matter.
I "think" I would go with the buggy. You could always get the hyper 7 and if you want more speed, go with the 2 speed kit:
http://www.nitrohouse.com/p9834/OFNA...duct_info.html
Then you have something about as fast as the jato and tougher and the price would wind up about the same.
Honestly, you are just going to have to decide for yourself. We can tell you the pro's and cons but you need to get the one that will make you happy at the end of the day.