If you play vanilla SH3 then you are missing out on everything good. Vanilla has nothing to offer. Nothing.
If you want an answer to your question, go back and read this entire thread.
The read this one.
http://www.subsim.com/radioroom/showthread.php?t=181798
And this one.
http://www.subsim.com/radioroom/showthread.php?t=191523
And this one.
http://www.subsim.com/radioroom/showthread.php?t=164880
And this one.
http://www.subsim.com/radioroom/showthread.php?t=190142
And this one.
http://www.subsim.com/radioroom/showthread.php?t=190995
And this one.
http://www.subsim.com/radioroom/showthread.php?t=189825
And this one.
http://www.subsim.com/radioroom/showthread.php?t=190140
And this one.
http://www.subsim.com/radioroom/showthread.php?t=186063
Then you'll get close to an answer, which is that it all depends on what you want. If you want spectacular graphics, the ability to walk around the whole u-boat, true real navigation, then SH5 is a good deal. If you want to drive a Type II or Type IX, have a free-roaming campaign that lets you sink more than one hundred different types of merchant ships then stick with SH3.
SH5 is great, but still lacks some major campaign functions that may or may not ever get there. Once I have a decent computer I'll play both. No, I'll play all three, plus SH1 and Aces Of The Deep.
Everything you hear or read will be opinion. There is no fact, no "this one is better". SH5 is cheap. Spend the five bucks and decide for yourself.
Oh, and get some mods for that SH3. You have no idea what you're missing.
