"DMA/MM nonsense" you say. I too am a client of CMC(Market Maker), only because they offer much better margins on a number of stocks than the other provider I use, MQ Prime(DMA). But when MQ Prime offers the stock I'm trading at the margin I want, I'm all theirs.
I'll give you my most recent experience to explain why. Yesterday before the close I went long (using CMC) on CPU at $8.83. It took a bucket load of dicking around to get it at that price though. The market spread was $8.80 to $8.83 with plenty of depth at the offer price for my means. Whenever I tried pushing the order through I was requoted at $8.85. This is a real irritation to me and it will certainly hurt the unwary.
So when you say "DMA/MM nonsense", I strongly disagree. One needs to consider the differences and what effect they can have on your portfolio.
Another significant difference I forgot to mention is being able to participate in the 'after market' auction. This is generally only available through DMA providers. I've filled incomplete orders through this facility a number of times.
The differences are hardly "nonsense".
By no means am I pushing any particular provider. They all have their pro's and con's. Keep your options open to both alternatives.