I've pretty much standardized on eneloop myself. I still have some old NiMh batteries, some as old as 2001 that the maha charger has recovered and they now run things like kids toys.
I use eneloop in all my prep gear because I never let it sit for years, I make it a habit to pull it out once every few months to test it and make sure it still works so at those times I just top off the batteries charge.
I haven't tried rayovac since I canstill get the eneloop for the same price.
A small note on the MAHA c401, its fast setting is actually a little too fast getting the eneloop a bit warm which could reduce its lifetime a little. I try to always charge on the slow setting and reserve the fast for if I really need a spare set charged up right away. I try to keep two sets of batteries for every peice of gear I have, I need to get a couple sets more for my wife as the spare for her digicam became the set for her breast pump so when we were away from home for a few hours one weekend I did use the fast mode to keep up with both. Once I get a couple more packs so she can have spares then I can slow charge one set while the other is being used.
I plan to pick up a second c401 soon so I can charge 8 at a time. I had an old rayovac charger that I paid $30 for from wamart and found that it didn't fully charge which partly led to my older batteries not working very well. I have some from 2001 that probably didn't even get 100 cycles before acting like they were worn out. The MAHA charger has brought them back to life.
I've standardized on AA's for many years now refusing to buy a digicam or anything else that uses propritary batteries if there is soemthing that uses AA available. I;ve found that with propritary packs after several years the cost even to rebuild the packs usually exceeds the cost of just buying a new peice of gear.