I've not heard any of the other GR07 variations personally, but it's my understanding based on others impressions between them that the BE is fairly similar in terms of quantity to the MKI (perhaps slightly more), but it's the quality that's said to have been improved upon. It makes for a very natural presentation, the lower regions aren't overly present when not called for - it's less 'analytical monitor' and more 'warm and fun' overall. I think it serves well for the purpose of 'good quality bass' over 'traditional basshead' for it's price. It doesn't seem to sacrifice the strengths of the other variations, as it still retains what I'd consider a lush midrange and high detail retrieval.
On another note, how would you compare your W4 to the GR07? I've been looking into multi-BA based IEMs lately (possibly cIEM) and the W4 was on my shortlist.