Well the reason people say that the vxl motor is better than the 4600 is beacuse you can gear it higher and stay cooler. Traxxas does over 70 with the rustler because they can gear the hell out of the vxl motor while still staying cool on 3s. I have had many castle motors and i can say that they are nothing special. They get very very hot for me with gearing as low as i can and using regular tires. I have had about 3 of them and they all get hot, one of which the bearings became ruined after about a year. Once i got the vxl motor, there was no going back. I love this motor and you can buy spare parts for it and stuff. You can buy a rebuild kit for it and even a rotor. I have geared my stampede 23/76 and with masher 2000's with a 3s and it did not get hotter than my 5700 on 16/90 on a 2s. Plus the vxl is 5 bucks cheaper, save yourself the money and get the vxl.
By no means am i a big traxxas fan either but they have made a pretty good motor.