Well you could've limited it to 2 choices really.
There's little to choose between them; any club would view the season as a sucess if they won either.
The Premiership is all about consistency and beating 'lesser' sides week-in-week-out, whereas the CL is about raising your game against the 'best-of-the-best'.
However, I voted for the Prem. (and I'm a 'pool fan btw) as, over the course of the season, you can't get lucky to get through a particular round, which is possible in the CL (and no I'm not referring to the semis against Chelsea - totally deserved

).
I do agree with Kaz though that the CL has more cachet.