If a game has two routes to choose I usually start with corruption, as I prefer romance and want to continue further down that path, but still want to see what the corruption route entails.
I like both routes romance and corruption but it depends on the game how far the corruption goes but ya i usually play all routes for most characters since i enjoy both
I quite often play two paths in parallel, if I see there is different content. I sometimes replay games because I like them, but I don't usually replay to see 'other' paths.
As for what I like, a bit in the middle, depending on the personality of the LI. I don't like romance path to be too mushy, I don't usually like when things go too dark. I like corruption paths when it is 'loving' corruption, discovery, I don't usually like degrading. The exception being some 'punishment' paths to 'bad' characters, when it is well written.