In reply to i.munro: Back to the original question.
With the exception of font6a+ <> V0-V3 which should probably be V1-V3, I can't see any great issue with the table.
It certainly tallies with my experience of both systems being very vague in their own ways. Everyone seems to accept that at Font the low 6s can be very variable and hence the application elsewhere is also hard. Also my experience in Bishop was that V1 & V2 covered a vast range of difficulty.
- On with the general dabate...
My main issue with Font grades below 7A is basically there are TOO MANY of them. In Font you have 8 grades of difficulty between 5 and 6C+. In V grades you have around 5 (V1-V5) and in UK tech grades only around 3 (5c-6b). It may just be me, but I think that 5 jumps in difficulty provides around the optimum for climbers to grade with, understand and hence use and discuss easily. UK tech grades are not bouldering grades, but are a bit too wide anyway so aren't a solution. Conversely with Font, due to the 'narrower' grades all I feel happens is that the grade boundaries get really fuzzy and I can never really feel certain what Font6b+ for example should feel like.
It's weird but I know exactly what Tech 5c feels like, but I still get a bit woolly with the 6a/6b boundary. I've got a good idea of exactly what Font 7A feels like - I've failed to link enough of them, but I can't really nail down where things fit in between 6B and 6C+. However, when it comes to V1-V5 I can say with a fair degree of certainty which grade a problem is, and how it should feel at that grade.
Basically V-grades are a new system so it should come as no surprise that the jump between grades may be a lot more 'natural' and suit modern climbers better than systems that evolved many decades ago.
Hope some of that makes sense.