i need store info on osaka as well! thanks =]
Kinda depends what you're after.
If you're looking for international brands Tokyo wins by a long shot.
What Osaka offers is a lot more "street" Japanese style fashion. And you'll find street in Japan is very diverse. From the gyaru style, to the hip-hop varsities and new eras.
In terms of electronics and gadgets, Tokyo has Akihabara - absolutely massive and crawling with annoying otaku alike.
Osaka has Denden town - which to be perfectly honest is better in every way. Prices are a lot cheaper and you can find a lot more things - whereas Akihabara tended to be loaded with anime/videogame paraphenilia and ......hentai...
Hope this helped.