I had a friend recently cancel MCM for AnimeNorth instead, even though MCM is arguably much bigger, as it's pretty overrated. MCM is basically THE even of the year but also very much a lobby con- you go because everyone else is going, but not everyone pays entrance to the halls.
Artist sales are good- if you don't make your money back at this con you're doing something wrong, and footfall is AMAZING, but also the general opinion is that it's full of poor teenagers. Some people do make bank but personally, because there's such a wide mix of people ("MCM" stands for "manga comics media", so it's an anime con and a comic con) I tend to find it's not my best event of the year. It's also horrendously busy (which can't be helped- the ExCel is pretty much the biggest venue in the UK) and there's a lot of bootleg, so the other stalls always seem a little underwhelming. Staff are OK, but they use a lot of young volunteers which is a little grating given how much money they make- they could afford to pay at least minimum wage.
However I'd personally avoid applying to CV (AA, this is £90-100 as opposed to £300-350 for dealers), as there is a blanket ban on fanart. It also always has the same core group of artist which makes it a very closed and often bitchy community which is sad as at one point it was a very exciting place to be.