На какие ECN ставить ордера ?

Electronic Communication Networks (ECN’s) - an electronic system for the implementation of transactions for the purchase and sale of exchange commodities, which tries to eliminate the role of intermediaries. ECN connects leading brokers and individual traders with each other, so they can trade directly, bypassing the exchange mechanisms of intermediaries. Always used ARCA and SDOT before , but there are many other ECNs in the LASER trading terminal, but no SDOT. I would like to know through which ECNs it is cheaper to trade, except ARCA. Which ECN to choose for market orders, where is it cheaper to hit the quote ? На какую ECN ставить stop ордер для NYSE, NASDAQ, ETF