A pair of Greenbacks or Creambacks will remove the ugly mid spike you get from V30's.
On the other hand, that same speaker has a good amount of cut in a dense mix, and records well. Everything's a trade-off.
Celestion actually was aiming to copy the sound of their old Blue G12 with the V-30, using one of the earliest laser/doppler things back in the 80s. While the overall tone shape is similar, obviously it doesn't sound the same. But the lower mid boxy thing was what they were going for. That edgy quality is really where the speaker is acting almost as a resonant filter at the point where the high frequencies start to roll off IMHO.
The Creambacks definitely have a more open sound.and what I perceive as a brighter high end. I am not sure I'd want that sound in, say, a closed back cab as much as an open back cab where it can diffuse the tone a little more; a lot would depend on the design of the cab.
Here's Celestion's own comparison of the V-30 and Creamback.
https://www.youtube.com/watch?v=ImfwNLCC5Uk
In this comparison, and with this kind of overdriven tone, I kind of miss the boxier, more filtered tone of the V-30; when the Creamback comes in, it is clearly more open, but also has a "screaming high end" kind of thing happening. I might prefer the Creambacks in this particular rig on clean tones, though. It depends so much on the amp and what kind of music you play with all this stuff, doesn't it?
Of course, a lot has to do with how you set up the amp and guitar. Seems there are never easy choices, it's always a matter of "pick your poison" because the permutations are so incredibly varied and tastes are so personal.
I've always found greenbacks a fairly dull sounding speaker
except in a Marshall style 4x12, where I pretty much love a good, broken in set.