For those looking for a little science behind why IMR batteries are better:
typical Li-Ion batteries, are made of Cobalt (LCO). These are the batteries found in your cell phones, laptops, etc. are made for high capacity (mah) uses, and in turn have a steady voltage. Cobalt itself is a very unstable substance that can explode in certain conditions.
IMR (LMO) Li-Ion batteries are made of Manganese, a very light metal that can sustain either extremely high (in battery terms) or extremely low temperatures making them ideal for high drain or variable voltage situations. LMO batteries are developed by the Japanese and are sometimes used for Solar Energy cells.
more information on these different batteries can be found here:
What exactly does "IMR" mean?
tl;dr don't cheap out and buy non IMR batteries.