You also forget that the brokers your listed above are by far some of the largest, meaning that the chances they will have a complaint are much higher.
There can by definition not be real ECNs in Forex so I prefer to go with No Dealing Desk and especially FXCM since they are much larger than MB. Makes me feel safer about my funds.
Actually FXCM offers 400:1 - they don't advertise it but all you have to do is ask and tell them if they don't give it to you you're going to someone else :D