I thought they would be similar because the fabrics feel similar. But the BG hardly held anything and felt *soaking* on a small baby soon after it was wet. However the TB Stretchie feels nearly dry even when it's soaking - don't know the difference, but it def feels a LOT less damp. And holds prob 2 to 3 times as much wee! Def go for the Stretchies - they're way better! You'll not be disappointed!
I use Stretchies on my 4mo and my 2yo, and another positive about them is the size 2 (BTP) ones fit both of them, so saves a LOT of money, as I think the BG are sized, so you need at least 3 sizes of them. And they dry a lot faster than the BG too! I have one BG fitted and hardly ever use it - just doesn't last any time at all, and takes ages to dry.