First of all, according to Hitman's thorough and documented PDF "German Optics," U-boats commissioned during the war did not have a stadimeter, only a graticle for angle measurement. You can find "German Optics" in the documentation for the
Hitman's Optics mod, available at Plissken's site. (
ftp://hartmuthaas.no-ip.org/public/S...3COMMUNITYMODS). Username and password can be found on this thread:
http://www.subsim.com/radioroom/showthread.php?t=171019. Hitman has done quite a bit of research, including actually looking at existing WW2 U-boat periscopes. His work is sometimes ignored, but I have never seen it disputed.
As to the question of which method is historically accurate, I believe the answer is "Neither." My sources are largely first-person accounts from USN fleet boats, but they are supported by the descriptions in Herbert Werner's "Iron Coffins" and the approach and firing procedures seem to have been very similar.
The first thing to remember is that the approach party consisted of, all told, perhaps a dozen officers and senior ratings, all with specific jobs to do. Much of what the gamer is asked to do was not done by the boat commander. The two methods OP describes were actually both used simultaneously. From the moment of first contact, the plotting party would be updating the attack plot with the most current information and generating course, speed, and zig-zag pattern estimates. Some of the plotting party's function is built into the automatic map updates, but not all. Of course, the plotting party was neither perfectly accurate nor instantaneous. But they did derive a target speed, for example, which is a task left to the gamer.
The approach officer would feed visual data to the identification party, which would try to determine the target's identity. But this was frequently not resolved in real time. Ned Beach describes an engagement where the target identification was decided 24 hours after the target had been sunk! So target ID was not needed for a successful attack. And agian, while there was a team to make the ID, they were neither infallible nor instantaneous.
The Approach Officer was usually, but not always the boat commander. Doctrine in both USN and KM called for the skipper to make all periscope observations, but that was sometimes ignored in both navies. And KG doctrine called for the 1WO, not the Kaleun, to make all target observations with the UZO during a surface approach.
The Approach Officer would estimate range, aspect, and speed independent of the plotting party data. (Hitman describes how these measurements were made.) The observations were fed into the TVR (TDC in USN parlance) and used to generate a solution. This was then checked against the plotting party's results. If there was a discrepancy, the skipper would determine what to do - make more observations, use the calculated data, or use the plotted data. A wrong decision would lead to a failed attack. There are plenty of descriptions of these in the first-person accounts.
So what do we have? If you do not use full automatic targeting, the gamer is asked to perform tasks the Approach Officer never had to do. The gamer usually has tools the Approach Officer did not have or did not use - stadimeter, 10x scopes, speed measurement function. When the gamer uses crew assistance, that assistance is much too accurate and much too prompt. And there is often no opportunity to determine the firing solution by multiple means and compare the results before attacking. The game is a game, and even with 100% "realism" (sic) and mods to enhance the fidelity, it is a surprisingly inaccurate simulation of the role of the submarine commander during an attack.
So, what approach procedure should you use? Whichever floats your boat. None are historically appropriate. I'd suggest reading some first-person accounts to get a feel for the activities and the atmosphere. Then pick out the elements you feel best recreate that feel, and use them. Experiment and choose what you like. There is no best answer and certainly there is no correct answer.
Nowadays, the Navy has what they call a "position trainer" which allows you to perform all the tasks of a designated position with the trainer doing the work of all other positions in real time. SH3 (SH4 and SH5, too) is not such a creature.