The facility to place orders direct, through the LII screen, is one of the great advantages of Nas direct access trading and each ECN has its own nuances which can be picked up from its site. Remember though that whether or not you can enjoy all the facilities an ECN has to offer (eg the trailing stops on Arca) will depend on the broker you use. IB, for example, is just not good enough to take full advantage of what "LII" has to offer. Equally, now Island has been absorbed by Arca the distinctions are beginning to blur.
Order routing is not, normally, an issue and IMO in the majority of instances a 'smart' order will work just as well. It is only in extreme circumstances of, say, collapse when the ability to use, say, a SOES order direct might save your bacon.
For me, one of the big advantages of LII is that, inter alia, one can see the thickness of the other side of the market so it becomes possible to take low risk trades knowing one can get out with a stop of only a few cents if things go wrong.
It seems to me, if others agree, that a thread on Nasdaq Level II may be of value to members. Grey and Paul are well versed in it and, from Paul's posts, I think I must have learned my Level II skills (such as they are) from the same tutor.
I presently trade Nas stocks using simple (non indicator) T/A to find opportunities then use LII & time & sales to enter and manage the trades. If what knowledge I have is of any assistance to others I am more than happy to contribute my two penn'orth.
It looks to me as if a VWAP methodology overlaid on what I do at the moment could turn my presently profitable - but sometimes hairy - trading into something rather less risky hence more relaxed.
I look forward to it.
If only I caould find a copy of Tradestation at a sensible price!!!!!