First, read this: http://www.airsoftcanada.com/showthread.php?t=99899
Once you've read that, a balancer ensures that all your cells are at equal voltage. If one is .2v higher than the rest, and a wall charger like the one you want is used, it will over-charge the LiFePO4 battery and cause it to burst into flames.
Second, a good charger will do both, and you should absolutely buy a good charger when your using lithium base batteries. You want a digital smart charger and nothing else, don't spend less than $80.
And there are two advantages to using lithium batteries, they have excellent energy density, and they are INEXPENSIVE. It has to do with the ease of manufacturing, but yeah, they are around $10 for a mini battery, and $40 for a high quality large battery.