I have shopped at the Fashionoutlets in Vegas and found it excellent value. All the top retailers are there; Ralph Lauren has an excellent store including home stuff. Tommy, a good Timberland, nautica, Nike, Addidas, GAP and many more. It is a 10 minute taxi ride from the Strip, so you can shop, drop your bags back to the Hotel, and go again the next day if you want.
I have been to SF but have no experience of Outlets there, they may be a long way outside the city, like in NYC.
The Fasion Mall Shopping Centre (Next to Treasure Island) are regular shops, but its a great centre. The Macys there has excellent value. There must be 100 stores in total and all give great value....Apple, Banana republic, Gap, J. Crew etc etc
I really do recommend Vegas shopping.