The 4500mAh 30C pack will offer greater punch and more runtime, but will be limited to a 4.5A (1C) charge.

The 3300mAh 25C Nano-tech pack isn't as powerful, but can be charged at 5.4 amps before your charger maxes out.

I'd stick with the hardcase (which you should be using in surface vehicles), it doesn't look like the softcase would have the capacity for extended runs.

4500mAh 30-40C 135A continuous, 180 peak, 1 hour charge (1C and 67 watts)

3300mAh 25-50C 82.5A continuous, 165A peak, 36 minute charge (1.64C and 80 watts)