I play SH4 as a Fleet boat skipper, not U-boats, because I've had a life-long facination with the US Submarine Service in WWII. I've studied and read extensively on the subject and its history for over 35 years. Currently, SH4 is the only subsim I can purchase that allows me to "experience" that history at least partially.
BTW, FWIW, I'm a "hardcore" PTO player and I'm interested more in historical accuracy than eye-candy...