We use BG v3s on dd, 8 months, which have aplix. As far as I know, pros and cons are:
Poppers - harder for little fingers to undo (although if you keep them covered with clothes, this wouldn't be a problem!), tabs less likely to look worn out quickly.
Aplix - far more adjustable, as you can stick the tabs anywhere, whereas poppers you're restricted to the positions of the poppers. Can also cross over the tabs if your baby is small. Downside is they will start to look a little worn after a while, although we've used ours since dd was 10 weeks and they still look ok. Aplix is also quicker to do up, which is good when baby starts to get wriggly!
Hope this helps. From a personal point of view, I also prefer the look of the Aplix ones, as I don't really like the look of all those poppers on the front. Haven't used poppered ones tho, so maybe someone who has can give more info.
In terms of choosing BG in general, I've been really happy with them, and also recently converted my sister to them too! (for her 14 mo dd).