I don't think you can really compare SH3 and SH4. They are really two separate games. I have been playing both for a long time. Sometimes I feel a little "u-boaty" and other times I feel a little "fleety".
The games are different from each other. Not only are the theaters of operation different but the gui's are different.
I am sure there are some people who like SH3 but not SH4.
I equally sure there are some people who like SH4 but not SH3.
To each his own. We fought wars to ensure that game players have the right to play whichever version of SH they want?
As for myself? I go both ways.
Uh I mean I like SH3 and SH4.