Rotor. Simple on/off (no programming is a good thing!). Simple dis-assembly for cleaning. Batteries last a year. Rock solid. My oldest one I have had for three years, before me it had at least two other owners. It has only jammed once, and that paintball was so malformed it would not have rolled through a paper towel roll.
The only negative is the capacity, and hell, I could solve that if I was not too lazy and/or cheap to buy the high cap shell.
My spool experience causes a little discrimination I suppose.
Ion: takes a half hour to do easy maintenance and there is a 50% chance it will leak once reassembled.
NT: requires at least a four year degree in metallurgy, physics, meteorology and dark magic to get it to operate.