Quote from Esq Esq Esq:
The big guys (GS, etc) are only useful if you're planning to get leveraged and if you want to trade accross multiple markets and have access to closed markets. Or need for a good prime broker if you are trading with the street a lot and have a lot of investors
Leverage is tough now with them anyway.
But if your looking to specialize - go to a firm that specializes in this.
There is no real reason to connect directly to NASDAQ if you are planning to trade on ARCA, BATS, EDGE, etc. Better to use a broker that is connected to all of them with minimal latency. They do all the hard work for you.