I guess it's a question of what you're looking for. I quite like the 'full' look they have on a gent's frame, with the slightly bigger diameter, wider rim and bigger tyre. But, I accept that the choice of tyres is limited - and they can be a pretty tight fit with mudguards. There's certainly no shortage of good 27" rims from the 70s though. I think I'd go 27".
I guess it's a question of what you're looking for. I quite like the 'full' look they have on a gent's frame, with the slightly bigger diameter, wider rim and bigger tyre. But, I accept that the choice of tyres is limited - and they can be a pretty tight fit with mudguards. There's certainly no shortage of good 27" rims from the 70s though. I think I'd go 27".