I have Lange and MMRS. I was only going to use Lange for Immuno b/c I couldn't find a decent immuno source, but I was pleasantly surprised at it's micro section. I really like how Lange gives the DOC for each bacterial infection after discussing the bacterium in detail. I also really like MMRS, b/c it's pics are a great memory aid. I haven't looked at RR, but I don't think you can go wrong with Lange and MMRS.