Personally, I've found BGS online to be more than adequate, I don't really believe in learning the QB pro-rata, as has been pointed out on my brush-up this month the exam QB in certain subjects is changing and people are being caught out.
The BGS QB is perfectly sufficient to give you an idea of the style of Qs you're likely to encounter. My 1st set of exams mirrored the style of the mock exams (I'm doing them in the UK, not sure how different the Irish ones might be) on BGS online almost exactly, a handful of the Qs weren't exactly the same as those in the QB (granted I didn't complete the entire thing), however having seen similar style of Qs before its easy enough to use the knowledge from the studies to arrive at the correct answer. The main issue with some of the Qs is the wording the examiner uses from time to time can be a little confusing, if you've had exposure to these and had the prominent examples pointed out to you, as they do at the BGS brush-ups, you should have no problem.
Good Luck
