Both Google Analytics and Google Adwords seem to have the capability of creating remarketing lists. If you opt for the Analytics option, you can then share that list with (only) Adwords. So are there any significant differences in functionality between the two options?
- You can use the lists via Adwords even if you do not use Analytics
- with Analytics you can use segments to create lists, which means that you have a higher level of granularity (which in turn means it's much easier to shoot yourself in the foot by creating lists that do not contain enough users)
Note that AFAIK remarketing lists are not yet available in Universal Analytics (even though the interface to create lists is already there).
Personally I'd use the analytics remarketing lists if possible.