We really like BA a lot - I would certainly recommend trying it. As for format,
we tried the first book/workbook (2a) for DD9 and DS6, then moved to online. The main thing I like about the online platform is the immediate feedback the kids get on each problem. This allows them to work much more independently than if I have to correct their work. On the other hand, I've heard a lot of kids enjoy just reading through the guidebook. It is online, but mine don't touch it. At least one of them would be more likely to pick it up if it were on paper.

You could always try the free month online first and see how it goes.