I have razors in the 4/8 to 6-7/8 range, none with barber's notch, and all carbon steel. Never felt the lack of a barber's notch - asthetic only? - but never had one, so...
I use different sizes for different jobs, so they're all good to me - I'm a pragmatic shaver. However, I've just ordered an 8/8 Friodur - in a few days I may have changed my tune!:)
James.