MMM combo is very reliable. No argument there.
Personally, I think the conversion kit you use is something that you should spend time researching. Personally, I am a HUGE fan of the Tekno Rc conversion. You can find it at Impaktrc.com. The reason why i'm such a fan is based off several things. 1) I like having a brake servo. The brake bias is something people will tell you that you don't need, but I disagree. Especially on shorter tracks, you can dial out some front brake and give the car a front one-way kind of feel. 2) It comes with a different chassis. These guys spent a lot of time figuring out how to put what where and it shows. 3)The motor mount is basically a giant heat sink with tapped holes for a fan. I love it.
Now, notice my extensive use of the word "I". Its just what I like. Watch different cars, do research and ask questions. Why 1/8 electric is so awesome is because there are so many different options. Whats best for me might not be best for you and thats cool. Good luck!