After several weeks with the 3 BEx earbuds, I find myself going back to the BE7. The BE7 is just clearer, balanced throughout the frequency range and sparkles up top. I find the BE3 slightly veiled from mid range on up. Plus the treble rolls off earlier than I'd like.
For $37 it's a great deal and a step up from stock. But because I have all 3, the sound of the BE7 is more refined and clear; justifying the $60 price difference.
I would choose the BE3 over the BE5 however, because it has a similar sound signature with the BE5 only slightly better. But not $60 better.
I normally use pandora and songza on an iPhone 4s and iPod touch (5) unamped with Yurbuds enhancers, for reference.