Read the thread linked to. We've covered it all and then some when it comes to batteries and chargers. Lipos are about 1/4th to 1/5th the weight for the same capacity and provide full voltage all the way up to the very end of the charge, so even a less capacity lipo probably will run longer than a nimh or nicad pack that is say 300 or 400ma above the lipo in capacity. Normal cells drop steadily in voltage as they discharge, unlike lipos. What that means is they are probably more likely to run into the low voltage battery alarm (around 10.5V or so) before the lipo does, even if they are higher capacity. I'm expecting my 750ma Rhino Lipo to probably match or beat the stock 1000ma rechargable nimh pack. In fact, I just cycled those new lipos to break them in and they are holding over 900MA, which is a good sign of a quality cell (holding more than it's labeled for).
Which reminds me....Kered, using the discharge function for lipos on the Accucel charger confirms what I thought. The thing doesn't monitor the individual cell voltage when they are draining, only when they are charging. What that means is I had a few cells dip below 3V by the time it was done. The charger can only manage a 1 amp or less discharge rate, and since these lipos are designed to handle 15 amps they are sneaking down under the 3V with the real low discharge. If they were being drained much faster they'd likely bounce back up in voltage some once total pack voltage hit the 9V cutoff. But then again, if you are draining them that fast it deletes the reason to cycle them in the first place- to gentle condition them with 3 to 5 easy 1/2 C or less charging rates and then doing an easy discharge on them.
If you are going to mess with lipos read that linked thread and pay attention to all the warnings. You must use a lipo charger and you should know the pros and cons to lipos. In a nutshell, never charge above 1C and never charge higher than 4.2V per cell or drain lower than 3V per cell. Never short them either. Their advantage is fast charge rate which is normal and fine for them- 1C which should take less than an hour, very high power densitity- meaning they are much lighter than nimhs or nicads yet hold much more capacity, and the fact that they hold their voltage high all the way to the end of the discharge. Another big advantage to them is that they can deliver very high amps, which isn't important with low detector amp draws but very important in the RC plane community.
I love lipos myself, and I expect you'll see some amazing range to electric autos in the future as the price drops on them and more car companies use lipos instead of nimhs or nicads. Lighter, much bigger capacity, good performance until the end of discharge, high amp delivering ability, very short charge time (1 hour). They've got it all. I'd expect if you took a lipo pack that weighed the same as a nimh or nicad pack the lipo would probably have 4 to 6 times the capacity, which equals longer run time. That's when electric cars might become practical. If I had the money I'd buy stock in any auto maker who is seriously looking into lipo technology and also is planning to buy from cheap sources. Depending on the name lipos can be very costly, but companies like Loong Max and Turnigy are making them at about 1/4th the price these days. A lot of power tools are starting to use lipos. Some are using variations of lipos that make them safer like A123 cells. Those come in metal canisters just like regular batteries and won't explode or catch fire if punctured, unlike a pure lipo. They also can stand being drained lower and have other perks to them. Several lipo type variations starting to pop up. LifePo Cells, A123, and a few others. All are considered to be improvements and are tweaked with various chemicals to perform better, stand up to abuse, or give longer life.
