I really enjoyed MMBN 3 - put about 40 hours into it, if I remember correctly. The version difference (white or blue, for 3) probably doesn't matter very much. You'll have slightly different rare chips/abilities that you can have in each version that are not in the other version. This encourages you to obtain them by linking up with a friend who has the other version.
Gamespot scores, I think, have declined from MMBN3 but largely because 4 and 5 are so similar to 3. I have been thinking about picking up 5 recently, since it is a fun game formula and it sounds like they have made some interesting additions.