GP's work for me. So do Powerex, Energizer, Nexcell, GI, generic green, generic blue and generic white.
I've never measured the cell capacity, and there might be a difference I haven't noticed. Other than that, all the NiMH I have just keep on working. Maybe all NiMH are made in the same factory, for all I know.
I've never had a NiMH leak, and I only had one die. That one got discharged to the point of reverse polarity one too many times. I think it was a generic green, but I don't think that matters.
I don't know about the charger though. It's important to have a charger that pulse charges, to keep the crystal size small, and knows when to quit without overcharging or overheating the cells.