Personally, after using all of the mentioned dictionaries, I ended up focusing on the two: OALD8 (since it is a de-facto standard among the Advanced Learner's dictionaries around the world) and LDOCE5 (due to its extensive database with lots of examples and pronunciations).
Interestingly, when I'm in a hurry, I prefer Collins

It has very precise and clean definitions.
P.S. Btw, I highly recommend that site, it provides *tons* of very well structured and interested content for those who'd like to study any foreign language.