Out of those three, Brave Maximus is the best looking IMO - not surprising as it's the most recent version. Takara clearly try to make the mould look better with each repaint -- Grand Max looks better than Fort Max. Fortress Maximus is the most plain looking of the lot... just so much grey. Brave Max's alt mode looks gorgeous, especially with the way they painted the windows to make it really look like an occupied city.

Interesting how theshape has them all displayed in robot mode. I have Fort Max in robot mode and Brave Max in city mode. If I had Grand Max I'd display him in starship mode. But that's just me. (not that I'm likely to ever get a Grand Max )