I have just changed platforms and gone back to visiting my subscriptions page. I do daytrade when the opportunity is there and would like to view market depth. But I'm not sure if all three are necessary: Nasdaq TotalView NYSE Open Book ArcaBook All of the above provide market depth, but I'm confused about some of it. The explanations I find for the above are unclear. Maybe someone can shed some light: 1. Isn't Arca owned by NYSE? Arcabook is "top of the book bid/ask last prices for securities listed on NYSE Arca and ArcaEdge". What do they mean by "top of the book"? Isn't that just regular level 1 bid/ask? And why do brokers want $10/month for this info? Are there securities that are only listed on Arca and not on the NYSE? Wouldn't the NYSE Open book already contain everything in Arcabook? 2. Nasdaq Total View is market depth for Nasdaq listed stocks and some other ECN's. Brokers usually want $15/month (same prices as the Nasdaq Data Store, and you get net order imbalance for free). Nasdaq Total View also displays market depth for securities that may NOT be listed on Nasdaq, by they just trade there. Will this include info from Arcabook? 3. NYSE Open Book is for view of the limit order book for all NYSE traded securities (note: not just for "listed" securities, but for "traded" securities). Won't this overlap Nasdaq Total View or ArcaBook? The total subscription price for all 3 is about $35. Not that material. I'm just curious to see if all three are really necessary. I know this all depends on what securities you trade and where they're listed. Any other opinions/info?