I think it does matter...
I think not all the question banks available online are the same... Of course lot of the questions that go around is common to all of the banks, but the rest of the data is what makes the difference. Some online sites do not have any updates in long, long time, while some sites are constantly trying to get the latest JAA questions into their databank. I'm involved in one of these projects (I'm not going to name which one to be flamed for advertising) and we were able to get the complete copy of the JAA CQB as of November 2005 along with the relevant picture supplements. I do not know of any other bank that has almost a complete HELICOPTER JAA question database (for the transitional period exams)... so anyway - in my opinion it does matter which databank you select.