If I may offer some additional thoughts, I am the trader in Steve Hopwood's forum who posted in reply to slowkey's thread on FSB. Regarding the use of broker data vs TrueFX or any other data import, my experience was that I learned to use FSB with Truefx import, only as a means to learn how to create strategies. Over time, with experience, I then learned the more fine points of the differences between TrueFX and other's data vs my selected broker's data, ATCBrokers. The data from ATCBrokers is a wholesale ECN feed. The only additional charge is from the Broker's commission as the rates are derived from the clearinghouse / liquidity provider.
I found it was most important to use tic data when performing testing, as opposed to end of bar data, as end of bar data could be misleading. An example could be a 20 pip spike in a bar, only for the bar to close negative and the trade to be closed at a loss. Having the tic data for analysis, at least for me, has been most valuable. My strategies are developed with signals (action) issued at the beginning of a bar which allows for the potential use of the full bar data . This allowed me to further develop a strategy which provides me with at least 1 period advance notice of pending changes in price direction.
If I am going to make proper choices for data, it is also most important to select proper broker services, and fees, as well as data feed. For consideration, I needed to monitor speed of fills, any concerns of MT4 modules on server to slow fills, is network ECN data or a modified "A" / "B" book where your trades are handed off based on your profitability or lack of?; Customer service actions / speed to address issues; Where are funds held? Any issues with withdrawals? Is scalping allowed? If so, any minimum requirements for time in position? Technical support of MT4 issues, what Hardware and Server backup capabilities are in place?; with regards to international routing - where are the servers located?; and other issues; How close is the clearing server to the clearing house? Is the data from the demo server the same data as the clearing server ( there is a difference with some brokers); Are the spreads on demo the same as spreads on live feed? If the phone system goes down, what, if any, alternatives for contact? These and many other questions.
So assuming the broker passes these questions, then I begin collecting the tic data from the broker. That tic data is collected and then converted to meet FSB format, which then is used for strategy testing. On each Sunday, before start of session, I analyze prior week of data for any changes in volatility, conditions etc. with reference to my strategies. If markets have unusual output changes, I will then modify data for use on a time period that will allow me to adjust to market changes. By being able to select my broker based on the above criteria, this gives me great confidence in the data, and should any issues arise, my ability to solve those issues quickly. (Note: I do not work for ATCBrokers and have accounts with them for 6 years. I know the owner personally and have additional support on skype and personal mobile).
I do run multiple strategies on multiple MT4 instances on systems which are separate from the development systems. I work with a large global group of traders as the Chief Market Technician, Strategy Developer and Trade Manager. I have been serving in the industry since 1998 and have experience as a top FX Account Manager / Market Analyst for a major Chicago based brokerage firm; acted as a advisory service to large fund, held workshops and webinars on TraderKingdom, and many other noted sites.
If I can be of service, please let me know.