For scale or for competition crawling? There really aren't any RTR competition crawlers anymore. As far as scale goes...it depends on what size you're looking for...most are 1/10 scale, but there are 1.9 and 2.2 size classes...which refers to the sizes of the wheels in inches. The "most scale" designation would go with the 1.9 size class, but if you're looking to beat on a rig that will go just about anywhere and will also handle some speed as well then the best bet is probably the 2.2 class. Here are the options as far as RTR go for each:
1.9 -
Axial SCX10
Axial SCX10 Dingo
Axial SCX10 Wrangler
Axial SCX10 Wrangler C/R Edition
Axial SCX10 w/ Deadbolt Body
Axial SCX10 Falken Edition
RC4WD Trailfinder2 RTR
2.2 -
Axial Wraith
Axial Wraith Poison Spyder
Axial AX10 Deadbolt
Axial AX10 Ridgecrest
As for which one to go with just take a look at all of them and see which one you like the looks of. Most of the Axial rigs in each size class share just about all the same parts so getting spares is really easy usually. All of the 2.2's share the same axles, but the chassis' are different between some of them.
I had a wraith and really enjoyed it...and spent entirely too much money on it. I've also had an SCX10 based rig and just lost interest in it. I prefer the competition crawler scene so that's where I've concentrated my collection. If you decide to get a rig be sure and let me know...I may be able to help you on the price.