Just go with separate brand specific chargers if you want both running at the same time...to charge two batteries you need two chargers.
However if you want a 'general purpose' battery charger, then you might want to look at the things used for RC racing. Many of these are microprocessor controlled, will quick charge quite nicely, can 'restore' overly discharged batteries, can measure capacity, etc.
I have had very good luck with the 'Triton' (
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCJG7&P=FR ) charger; I use it to charge NiMH and Li-ION packs for hobby use, and have used it to 'save' Milwaukee batteries (I discovered that if the packs are left unused for an extended period, they self discharge, and then the Milwaukee charger doesn't 'see' the pack. By using the Triton to start the charge cycle, the Milwaukee charger would see the battery and everything worked fine.)
There are many other such chargers.
-Jon
