Surprised I couldn't find a lot of info on this.
I'm exlusively trading on the DOM, currently via NT. But I'm a bit sick of it, it's rather basic and very little customisation options.
So I decided to look elsewhere and since I just signed up with AMP and you get Sierra Chart, Multicharts, Xtrader and more for free, I gave SC a go and am extremely impressed. I seems to knock NT right out of the park, and is much leaner at the same time.

Still need to practice with their Dom but I thought I'd put it out there.
Which Dom do you think is best?

I could not agree more. I think Sierra's DOM is far superior to Ninja. It is faster, more flexible, more feature full etc. My needs as far as order management are pretty basic but speed is important especially during news events. You can change the update speed on the DOM under chart settings - advanced settings to chart interval update. I set mine at 30 which is probably as low as you need to go. It is crazy fast. You can do the same thing on the chart. X-Trader and TT is also really fast and fine for my needs but it is pretty limited as far as ATM/Order management strategies unless you can create them in ADL.