Apparently gamepark use different memory suppliers at different times. Some memory lets gp32s run at 166mhz, other memory doesn't let them run quite so fast. All gp32s officially have a top speed of 133mhz. GBAx are now shipping GP32s with the free launcher etc already installed, so I guess that as part of that process, they're testing which ones can run at 166mhz without problems, and selling those ones as 'guaranteed 166mhz'. Yes, they'll eat the batteries quicker if used at 166mhz, but the speed setting is an option in certain programs, so they'll be jsut the same as another gp32 unless you choose to run them faster.