Speaking from my point of view as a woman- I found that a penis that erects to the 12 o'clock position can be less versatile. If the mans penis erects there and doesn't have much lee-way to move down to say.. a 3 o'clock position- it can make it harder to do other intercourse positions then just man on top.
Thats been my experience at least. We always made it work- but it could be frustrating when wanting to explore other options.
Just my 2 cents. Other women may feel differently.
In my younger days I was a '12' and have to totally agree.
Whilst it might have been an 'ego booster' it could be/was limiting and added to that the almost painful 'rock-hard' associated the supercharged hormones of youth, very uncomfortable, in some positions, for both parties - cowgirl and doggy.
I am now happily in the '2' range which can and does give much more 'flexibility' - in all senses - although I still get pretty hard (if 'pretty' describes it :)). I can also be 'persuaded', without any problems, into '3'.
There can also be another problem with '12', with a new inexperienced partner, that has nothing to do directly with penetration (although it might initially effect it) - her seeing how far 'it' reaches up your belly and her imagining how far it is going to 'reach' into her.
The so called 'average' 6" can seem quite long (look at a ruler and it actually is) when seen against a belly, whilst the more horizontal positions give less indication as there is no 'point of reference'.