4wd SC generally thrives on 8th scale tracks, but can also run on 10th scale tracks. I wouldn't even try running a 10.5 in a 4WD SC as today's 4WD sc's are all way too heavy for a motor like that to be happy with.

That being said, as to your connector question. Randy answered with the #1 reason, an extra failure point. But it isn't just a failure if it comes unplugged. They also create resistance and heat. The more you use them as hot swap plugs, the more they wear and the more they're likely to end up with dirt in them. Both wear and dirt will dramatically increase the resistance, which increases the heat, and also makes every other part of your electronics system work that much harder. On something like the 10.5, that wouldn't cause too much stress in most cases on anything but the motor. On something like a Pro4 motor, you can pull enough wattage that the extra resistance can very much overtax an ESC or battery.

If you do end up doing bullets for a motor connection system, use large bullets that are solid (not bird cage style). Make sure they're firm to press in and hard to take out, ensuring a good physical and electrical connection, and then wrap electrical tape around each one to hold it together and seal it from dirt before using it.