It kinda depends on what you're after.
The smaller MU line has had some great figures, but it's been pretty much DOA for over a year, with a few sporadic releases here and there of new product. Plus it'd mean a whole new scale for you.
ML has been really good. They really upped the quality of the paint and sculpts compared to when they first got the license. Distribution has been horrible though, and many key characters have been hard to get, due to a lot of 50/50 variants, and many variants not even making it to stores.
ML is heading down the line of following the branding of the movies. Theres' leaked lists which show upcoming figures for both lines, and we'll be seeing a lot of general Marvel stuff released under the Avengers banner. Okay fine. As long as we're getting new figures with decent quality, call them whatever you want.
Do you have a particular group/team/character you're particularly keen on, and if so, a certain era?
Looking To Buy Either Siege Or Earthrise Ratchet, and Buzzworthy SS86 ER Cliffjumper.