I have seen 3 brokers with all different tick charts from 1) TA 2) Barchart 3) OEC The biggest differences were in the opening and closing. This makes sense of course. None of this really matters though unless your program is dealing with very small timeframes / resolution. If you are just a "normal" discretionary type of guy none of this will really matter to you.
I would like the ability to place a trade with my mind instead of reaching for the mouse and clicking on the chart. http://www.livescience.com/health/050317_brain_interface.html