Originally Posted by Babboon

Umeda is more of a business district, it has the Sky building which is cool for the views, the stations there connect more directly to Kobe and Kyoto
Namba is more touristy/younger because of dontonbori, shinseibashi, amemura, shinsekai and nightlife. Also a little close to Universal Studios Park.

Both will have the same major stores like Don quijote, department stores, etc and Umeda also has a nightlife area as well just not as big or tourist driven.
Also they're only 4 subway stops away from each other (8 minutes) on the subway.