Ever I played SH4 - with mods - and it continues to be a very enjoyable experience. From the old times of SH1 I like PTO and Fleet Boats.
But also I playing SH5 with TWoS. I can secure you SH5 isnīt more the crappy incomplete buggie game of the early times. The hard work of the modders was awesome. The gameplay is a lot improved and the game have new functions - unthinkable in others SHs. I think - if you bought SH5 and have abandoned it - is a good idea to try TWoS and see the changes. It is another game.
Best regards!
Fitzcarraldo