| Hi HogF,
I have a (newer model) 750ss and a 748s. I'm 5ft 11, and less than 15 stone, (but not much).
To be honest, I don't find much difference in comfort between the two. The 748 does have better suspension though. Neither would be my no.1 choice for commuting, but if only 1 in 10 rides is commuting then they can both do it. I use the SS if I commute, but the 748 can do it as well. The real point is what you will be happy with on the other 9 out of 10 rides! You really have to try them both. I have to say though that I am really happy with the 748.
Has the 748 got a full service history prior to the 12k service? That's important.
Good luck. | 
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