If I were a betting man, I'd pick the LOSI LST. Due to the fact that the LST will out weigh the E-Maxx by maybe 15% and it diffenetly will have the gearing advantage over the E-Maxxx. The LST has low range, so the torque will be there right away. Anyone that has owned a real 4x4 with high and low range, knows how much torque they have in low range compared to high range.
Power wise may be close, but I'd thing the Nitro powered LST would have the advantage there as well. The longer wheel base on the LST helps it as well. I just don't see any advantage going to E-Maxx here. Tires should be a wash, if they are both close to a stock tread pattern, and size. A stock E-Maxx weighs about 8-9 pounds, while a stock LST weighs in at just over 13 pounds. Both will have added weigh due to beefing things up. So I'd guess it will be 12# E-Maxx vs 15# LST.