An ECN broker is what you SHOULD go with as there is no supposed to be any manipulation of pricing and they supposedly do not trade against you, aka take the other side of your trade. There are few retail ECN models to choose from, the top ones (US) being MB Trading, IB, and a few Currenex brokers such as PFG and FXDD. You will pay a commission based on dollar volume but should not have to deal with the various price spikes that dealing desks tend to have (do a search about this).
There are a few good dd brokers people recommend, the most probably being Oanda.
As to demo vs. reality, as you know, with any demo account, it is mostly about the trader psychology and risk tolerance. In a demo, the trader will sit with a position longer because it is not his money on the line, and that will skew the results. Also, with demos, you get fills when a price is touched - this ignores where you stand in line in order to have YOUR order filled, so that will skew results too. And with demos, you can always reset your results until you get the numbers you want.
Hope this helps.
Also, even in the fine print of your broker agreement, there is a little phrase that bugs people which says the broker is the counter party to your trade - this is true of all brokers unless you are a tier 1 player - if you are trading THOROUGH another broker, say IB, then they are the party that offsets the trade with DB or Citi, not you. You are trading thru your broker, not directly with the other banks. This tends to be a little misleading when ECNs say you trade directly with another party - you don't really.
