The maximum charging current will determine how long a charger takes to charge a battery fully. The balance between charging current and applied voltage will vary for lead acid, NiCd and NiMH batteries during the charging cycle.
The usual rule applies with any battery - if you're going to stick it in an expensive item, its worth getting a good battery, i.e. one with a brand track record and preferably with a guarantee against leakage.
Another vote from me for the Eneloop Pro's. They're hands down the best batteries I've used. I've tried the Powerex 2700mah, and they're not bad...but no as good as the loops. Another +1 for the Maha Charger, too.