I can't really add anything to what Ducimus said; he named all the choices, and they're all good ones.
There are four regular patches, just like in SH3, and the fifth 'pay-for' patch, which also adds u-boats and fixes several of the older problems.
You'll find SH4 to be a very good sim, with some improvements over SH3 which do make a difference. To me, anyway.
Welcome to the dark side.
