Depends on what you like really... SH4 is graphicly more beautiful but SH3/GWX has better game play and a better career IMO. It also depends on your preferences as to if you prefer US Fleet boats in the Pacific or German U-Boats in the Atlantic... I'd say give it try if you're interested.
Good luck and Welcome Aboard!
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GWX3.0 - SH3Commander - Thomsen's Sounds Pack - Manos Env Pro - Hitman's Optics - RB's UBoat Flags - Waterstream & Exhaust CombiMOD - Torpedo Damage Final - DiD
AMD Phenom II x6, 16GB DDR3, 2x NVidia GTX460 1GB, WIN7 64bit