I agree with IB and I have no intention to move from them as my primary broker. Prorealtime offer a sponsored IB account where you get a standard IB account, but commissions are slightly cheaper and you get the PRT software for free plus support from PRT staff. You get all the standard IB account, TWS and IB support as usual. As there doesn't seem to be any downside (that I can see) I decided to open a new IB account sponsored by PRT. It isn't possible to convert an existing account. My application has completed and the new account is waiting funding. PRT don't let you transfer funds from existing IB account to new IB account, so I have to pull funds from IB to my bank then back, which seems crazy. The real concern is PRT are now claiming one-click ordering is not available on their platform unless registered as a professional trader, and that is beyond their control as it is an IB rule. Clearly that isn't the case as I've been using one click trading, with hot keys, in IB for over 2 years. I've also been placing fully automated trades via the TWS API. As a daytrader this is a showstopper for me. I'll see how this resolves and keep you updated.
If you want to feed the data into your custom software, Nanex NxCore is hard to beat. Price will be $250-$300/month. I've been using them for a week and am extremely satisfied.
As I started this thread, I thought it would be appropriate to finish up. The difference I was seeing was in the way the client software was updating, not in the feeds themselves. So apologies for the wild goose chase. In the end I decided on Rithmic as it provides full depth of market, includes MBO data, and can be fed into multiple client apps via R-Trader Pro. Regarding ProRealTime, in order to enable one-click-trading you must meet at least two of the following criteria: (a) the value of the client’s portfolio of financial instruments, defined as including bank deposits and financial instruments is greater than 500,000 EUR; (b) the client has made at least ten transactions of significant size (minimum 600 €) per quarter during the four previous quarters in the market in question; (c) the client has had a job in the financial sector for at least one year that requires knowledge of the transactions or services they plan to use, or had such a job in the past for at least one year; PRT commissions are slightly more expensive than IB direct. Cost per Micro E-Mini is $0.52 per side vs $0.47 for IB. But with each contract you get a rebate against the ProRealTime monthly platform cost. I like PRT for charting and technical analysis, so I'm happy with the additional cost.