ive owned both eggs, and halos. my reviews:
had 3 eggs (just incase
)
reasonably quick, z board was much better but still not quick enough for me, reliablity was excellent, one egg NEVER brokw down in 1 and a half years. the cosmetic spares are cheap and easy to get, but internal spares are not available readily
Halo:
had 3. heard rumours of their unreliability. tried them out, had 2 V board and one z board, V35 board was my main used one. impossibly quick, loved the position it had on my gun, good weight, and held a good amount of balls, drinks batteries if you dont unplug them after use. i have had one break on me yet
the spares are hard to get hold of usually, but i found them really easy to fix just like an egg (im technically minded though)
if you have the money, go for the halo, awesome speed, awesome everything!