ISLAND or REDI For liquity, better price, speed.... Whic one is better for QQQ? Tell us about your experience using REDI & ISLAND...
Island has greater book depth and greater liquidity and handles more share volume. Both are extremely fast and responsive networks.
In addition, Island is the cheapest ECN. When adding liquidity to the book, they charge no fee; when removing liquidity from the book, they charge just .0025 per share.
I use Island (via my Redi of course), and since we don't have to pay ECN fees in either case, I "toggle" between the two at times. The "island guys" have made the market more liquid, but also more difficult in many cases (we loved it when we were trading with the AMEX, but then they got squashed by the Island traders).