You are correct,its all relative to our tastes.
The 6 in 1,Is a great Base as you stated...I would not suggest it be used outright as a sauce alone all the time,But straight from the can,to me,it was great.Was not bitter,nor metal tasting.
Interesting enough,when you mentioned Basil,I have been staying away from cans with added basil...I do not know why,I do not like the way the sauce mix taste from the can.I prefer the basil to be added fresh if its called for when making a sauce.
Sometimes added Basil or even other spices in the can already,the stuff taste a little bit "medicine" like from the cans to me.
I do not doubt the san marzanos,if the right cans are found,might be superior to the rest.The problem is,depending on where we live,and whats been labeled,sometimes we do not get the best or get knock offs.
Thats one of the reasons I made my thread here...cans I used before,I'm getting crappy quality now...do not know why.Had to keep testing to see what the other brands had to offer as well.Sometimes its a bad batch,sometimes it may be a supplier problem or canning problem.
We never know,they dont tell us.What matters is when we open the cans and see and taste whats inside.