5.5mm bullets for all my batteries. Deans are too small for my stubby fingers too, but the traxxas connectors just look abit cheap and bulky, like tamiya connectors, even if they are rated the same as deans. Im hoping there will be some more developments on the bullet connector housing front.
Deans for now until i get the MMM.
One thing i do to keep dirt and maybe even water out is to shrink tube (3-4" long)the two deans connectors together then neatly with a razor cut the shrink wrap around the base(wire side) of the female plug. This also helps the big finger guys by having the shrink wrap 1" down the wire on both sides for something to grab to separate the plugs.
Here is a picture to help, motors and esc were done this way.
Right now Deans on everything except esc to motor where I'm using 3.5 bullets on 18th scale and 4mm on rest. I've just bought 5.5s so those will go on anything I build next, repair or modify.