I wish Apple would make Tiger $99 instead of the $129 and $149 instead of the $199. I would like these prices much better, and they look better for marketing purposes. If one has bought a Mac with 10.1, then they upgrade to 10.2, 10.3 and now 10.4 that is $390 which is a good deal of money. I am not going to gripe, however, since I love Mac OS X and would pay more than $129 for Tiger.
Almost all are upgrading, so there would be no brand no difference.