In reply to no one in particular:
I think tolerance for both grading systems is the way forward. Each system has its own + and -. Overall, I prefer V-grades, just because I've climbed in areas that use them more frequently (despite living in the UK - Simon! Some people do make it further afield than Font).
Also, I've found that grades, despite whichever system chosen, have their own local peculiarities. For example in the lower grades that I climb, I've found Font grades to be much harder in Font than 'Peak Font' grades. I believe this is due to the general sand-baggy nature of Font and is part of the fun of the Forest. It almost makes the grades irrelevant!
I could say the same for Bishop V grades (hard) and the ones in the North Wales Bouldering guidebook (soft... er suits me). However when you look at their scales, you can see why.
I realise that it isn't necessary to translate back to Font grades, however, for the sake of argument....
Bishop
V1 ~ Font 4-5
V2 ~ Font 5-6
V3 ~ Font 6a-6b
V4 ~ Font 6b-6c
V5 ~ Font 6c-7a
V6 ~ Font 7a+
V7 ~ Font 7b
V8 ~ Font 7b+
V9 ~ Font 7c
V10 ~ Font 7c+
V11 ~ Font 8a
and so on...
NWB Guidebook
V1 ~ Font 5
V2 ~ Font 5+
V3 ~ Font 6a-6a+
V4 ~ Font 6b-6b+
V5 ~ Font 6c-6c+
V6 ~ Font 7a
V7 ~ Font 7a+
V8 ~ Font 7b
V8+ ~ Font 7b+
V9 ~ Font 7c (grades start to align here)
V10 ~ Font 7c+
V11 ~ Font 8a
and so on...
So for grades up to Font 7b+, both guidebooks give very different scales and might explain why one area feels harder for the grade.