Those numbers are right on, and LiFe is slightly more powerful than typical Nimh 6-cell packs even though it has a lower nominal voltage, because the voltage will not sag like Nimh does. Good Nimh packs may hold higher voltage than a LiFe 2s, but they will deteriorate at a faster rate and after 50 runs or so the voltage will sag down to lower levels. You definitely want to go with lithium packs of some sort, I would only use LiFe if I raced a class where I had too much power with 7.4V. They are a good choice for someone who does not want or need a power upgrade but wants the benefits of Lipo. I, for one, am always up for a power boost in any way I can find it!