proportions shouldn't make a difference. There are a few things that do though:
The actual volume of the tissue inside
The skin elasticity (you can be slightly larger but your skin may be more elastic and able to retract better than a smaller guy. If it isn't elastic enough you end up with loose skin where tissue once was)
Areola and nipple size (less can be done in the way of resizing with the peri so if you have big areolae your chest will look strange as females usually have larger areolae than males)
Nipple positioning (they are limited in how much they can move the nipple so not all chests will look natural, similar to issue above)
And of course, more personal issues. I think it is something like half of people who get the peri end up having a revision, and some guys just want it over and done with, and also peri costs more most of the time.
If a surgeon recommends DI then you should go with that if you are going to go with that surgeon (or you can go to a different surgeon who may feel comfortable performing the op on you).
I might have missed out a few things, correct me if I have
