Hopefully this helps some:
Novak systems which are easy "plug and play". These are sensored motors and will have no cogging. Being a smaller motor they compensate for lack of torque with a higher KV. Higher KV motors tend to run hotter. With the higher KV there are greater RPMs per volt, and as such you need to gear down much more, which generates the torque. Most other BL motors have a larger magnet which generates more torque, so you don’t need to gear down as much.
There are two motors which work well with the E-Maxx: the HV 6.5 which is better for bashing and the HV 4.5 which is better for racing. The 4.5 will have more top end. On 4s the speed controller may run hot and require some type of cooling such as a fan, body vents or heat sinks. I found one reference for the 4.5 of 750 watts of power and 40 oz of torque.
These motors will come packaged with a speed controller and are more economical.
http://www.teamnovak.com/
2. Feigao motors will have more torque than the Novak motors but can also run hot. Again, because of this inefficiency they may need cooling modifications such as fans, vents, heat sinks. The end bells are pressed on and may require a clamp to prevent failure. There are three motors which work well with an E-Maxx. The 8 XL on 4s, the 9 XL on 5s, and the 10 XL on 6s. I found one reference for the 9XL of 52 oz of torque.
http://www.feigao.com/sdp/85838/4/pl-102732.html
These motors run well with a Mamba Max speed controller. The MM esc is programmable and has more setup options then the Novak and therefore it gives you greater control. However, above 3s it will require a battery elimination circuit or bec.
http://www.castlecreations.com/products/mamba_max.html