Personally couldn't make do with any one particular region, I look at aw (all regions) and if I see a profile I like figure out how to get there.
I seek out what I consider mainstream model types and for them London is better for Brit girls in their 20s, sa and international sp's.
However, nw I've found is much better than London for gym toned brit milfs and under 23 sp's of my type, plus other regions are a short drive away.
The fact London has a higher quantity of sp's, should make it the winner all round, but the amount of sp' that fit the bill of what I seek, i've historically found to be significantly lower in London for the young ones and milfs. For which I've got no explanation.
What constitutes best punt varies, from my thing, to kink, trans, chubby chasers etc so there's not a one size (region) fits all answer.