The 0610i is a better charger IMO. It's more powerful so you can charge higher cell counts without having to drop the current to fall under the 50W cap on the 0606i.
Also, be sure and check out the new Trakpower 3S 4900mAh packs that will be out very soon. You can check out some info on them in this thread:
http://www.rc-monster.com/forum/showthread.php?t=10035