Kind of sad that Beckham is going to the US next season. This means it'll be difficult to see him on TV playing soccer. And by doing that, he unofficially say goodbye to top-level league soccer and international competition.

The options of staying in Europe are not quite attractive. Right now, the best leagues in Europe are English, Spanish, Italian and German. And by going there, you would probably want to join the top 3-5 teams, i.e.

England: Man Utd, Chelsea, Arsenal, Liverpool
Spain: RM, Barca
Italy: Inter, AC, Juventus
Germany: BM, WB

Going back to England is obviously the top choice. I'm sure a lot of MU fans want to see Beckham returning to MU. And it won't be difficult for him to find a place on the pitch. But reconciling with his former boss seems to be almost impossible. After being such a prominent MU player, you will not want to join any of the major rivals. Also it is not that easy to survive in the Spanish and Italian league, given his style of play and language barrier. In fact, there aren't too many English player who can survive there.

It's still possible to join some tier-2 teams. But do you want to take a thinner paycheck, not being able to compete at the top level, with lower chance to make the national squad again, but putting in the same amount of effort????

Going to the US is a wise choice. I would probably do the same if I were him. The benefits I can think of:

-the fattest paycheck a soccer player can ever get
-living in an English-speaking country
-living close to hollywood
-playing in a mediocre league may not be very enjoyable, but anyway have fun