Most are not going the way of the quad rail due to weight. Not to mention you will need to buy covers because if you don't, you are going to ding up your picatinny rails.
I also like the look of M Lok myself and it's much lighter than the quad rails that I owned in the past.
I'd look for MI if you don't want to spend too much.
What is your budget? There are some $20 quad rails I've seen for sale lately...most are no name brands, but they will work.
Also, the quad rails can snag on clothes and gear if you don't have rail covers.