amerelium

I've posted a detailed comparison in here when switching from Yam to Suz 350:

Yam F350 - Suz DF350: final direct comparison.

kmoose

Big heavy boat without question goes to the DF350. Faster to plane and at much lower speeds with the duoprop and excellent fuel economy. First ones out had some lower unit seal issues that have been rectified. The Merc 300s would be my choice for triples or on a smaller boat to replace other 300s. So far they have been pretty solid with only a few isolated issues. Price is going to be the big factor. You should have no problem getting a pair of DF350s rigged under 50k where as triple Mercs would be considerably more.