[BrianG]

I'm sure each of the chargers listed has its pros/cons. Since I don't have the other two, I will comment on the Xtrema:

Xtrema Pros:
- 10s @ 8A
- 4 pack memory to choose from.
- Ability to set the CC/CV threshold from 3.6v/cell to 4.2v/cell in 0.05v increments. Good if you want to lower the peak v from 4.2v to 4.15 for longer cell life. Also useful for a 3.7v "storage charge". However, the safety cell verification algorithm uses a 3.0v min cell value to verify the cell count entered for all CC/CV thresholds except 3.6v/cell. That one uses a 2.0v min cell value (specifically for A123s).
- Built-in watt-meter
- Firmware upgradeable.
- Optional balancer system that is very versatile.
- Temperature probe.

Xtrema Cons:
- Lithium only. Would be nice to charge NiXX so only one charger is needed. The maker says this was intentional for safety reasons and there probably isn't enough firmware memory to store a whole different charge profile. That said, you CAN use this to charge NiXX with a little creativity using the temp probe as the peak detection.
- 180w power limit, but they are thinking of raising the limit via firmware.
- Only 4 pack memory. Would be nice to have more.
- No discharge function. No big deal really since this would only be used to drain lipos enough for long-term storage. Better to run the pack in a vehicle and use the storage charge feature.
- The optional balancer solution quite cumbersome and expensive for multiple packs.
- Firmware upgrade possible via special cable, which is extra unless there is some type of promo going on.