For my 2p worth...
Personally I like both O/U and S/S shotguns. My preference is for O/U for 20bore and smaller and S/S for 16bore and 12 bore (if ever I get a 10bore it will either be a pump or S/S). This is partly (mainly?) due to aesthetics, but also I don't like the wide gape when chambering the fatter shells in an O/U.
I don't have any first hand experience shooting an O/U double rifle, but I like the idea of e.g. the Heym in 9,3x74. However for a 450/400 and up I would personally stick to a S/S - for the same reasons as above...
Oh - and I hate single triggers!