I've owned three Yanmar 6LP's and they always ran like a top. A little busy with the extra relays and price parts are not friendly on your wallet.
I now run twin Cummins 6BTA's - no timing belt (6LP is a timing belt engine, 6LY is not), a simpler engine to own and work on, and parts prices are much more tolerable.
I'd take either one if maintained to a high standard and setup right as to prop load and a safe exhaust system.
If you want that definitive answer - Cummins would be my first choice.
Where else could you get support like this:
https://www.sbmar.com/
https://www.sbmar.com/community/
Rob S.
"TENACIOUS"
1974 Chris Craft 36' Commander Tournament
Cummins 6BTA 330B's
(Former Owner)
"TOY-RIFIC" 2000 28TE, 6LP, Hull 408
Luck is the residue of good design.