I know that pprune is quite UK biased, and that might be the reason for Bristol QB being the favorite. ;-)
But not all countries actually uses the new(est) syllabus. DK is still on the 1999 one. To my knowledge jaaqb is the only QB that implements all syllabi.
Still, the very best way to use a question bank is to actually know why you answered what you did, and not just memorize the questions and choose "D" because that was what it was the last time....
In that respect, a question bank with a good feedback system and an easy way to save the questions giving you trouble would be my favorite. And I like that I can practice one group of questions at a time...
If Bristol works for you, stay with it.. but I think there are many cheaper and better alternatives out there...