The PDQ 36 is a catamaran that was offered with either twin 10 HP
outboards, or twin Yanmar 2GM20's with saildrives (18HP). We chose
the diesel version, but about 2/3 were built with the outboards.
Actually, for those that had a choice, it was probably more like a
60/40 split.

The outboard versions are faster sailers because the the outboards can
be raised to eliminate drag, they weigh about 600 pounds less (the
actual difference is even larger because the diesel version got a lot
heavier fittings all around), and the weight distribution is better
with the outboards mounted a bit forward of the diesels. The
outboards are certainly cheaper initially, and have the maintenance
advantage of being easily removed. Last year we watched a sistership
on the next mooring replace an engine in an afternoon.

On the other side of the equation, although my diesels sail a knot
slower (its still faster than most monohulls) it powers about a knot
faster. Although the 4-stroke outboards are pretty quiet at low
rpm's, at wot they are very noisy and there's no easy way to
soundproof them. Properly maintained, the diesels should last 4000
hours or more, but the outboards tend to cook in 1000 to 1500 hours.

The final factor for us was the need to generate power - we would have
had to install a genset to supply our needs, and that tended to even
out some of the issues. I've thought about it a lot over the years -
if I had to do it again I might live without the freezer, reduce the
electrical needs, add some wind and wind, and get by with a small
Honda genset and the outboards. But then I talk to sisterships who
carry two Honda's, and three outboards and I'm happy I have the diesels.

One more thing -
With the current cost of fuel, the diesel has an added advantage.
Powering 100 hours a year, diesel would cost about $250 a year.
Powering the same distance with gas, however, will cost more like $800
at today's prices. If your need is to power out of the slip, the
outboards are fine. But a trip down the ICW will cost a lot with gas.