I just upgraded from my old Spansion S25FL512SAGMFI011 (64MB) flash chip to the Micron N25Q00AA13GSF40G (128MB) flash chip. This lets me hold twice as much sample data. 64MB is pretty close, but I found that when you have multiple kits defined, and when wanting to have access to different sounding cymbals (all at different velocities), that having more space gives you more options.
Performance wise, the new chip is much slower to erase / upload samples (erasing alone takes almost 10 minutes), but when you are reading from it, things are just as fast as with the Spansion (which is what matters - erasing will happen only once in a while).
If you are following along, please note that the pinout is slightly different than the Spansion. In particular, the Spansion has internal pullups on W# and HOLD#, whereas the Micron does not. You need to pull these pins high for it to work. Also, the Spansion had a second voltage supply (VIO) on pin 14, whereas the Micron's pin 14 is DNU (Do Not Use). On my board, I just used some jumpers to connect VCC and W# / Hold#, and bent pin 14 up so that it was not connected. Yeah, it's a hack, but it works.
Now that I have the extra space, I need to go through my samples again and pick out ones to fill it up! ;-)