I can not comment too much on the e-tec. I have heard half the people love them half the people aren't too happy. This is from multiple people on the service side.
The suzuki I have heard very good review when they run. They turn a bigger wheel, are powerful for the rating/displacement/weight. Guys say the are very reliable
The problem in my area (Long Island) is service. I have heard horror stories about getting parts and waiting multiple weeks. The few guys who do service them are always back logged with work.
The Yamaha I have hundreds if not thousands of hours of personal experience with. The F150 is powerful strong inline 4 design. Very fuel efficient. Service and warranty are top notch. You could get the motor worked on and get parts in Africa if you needed to.
Out of hundreds of Yamaha F150's we sold and serviced I only saw 1 blow up and need to get rebuild and it was most likely user error with the owner beating the shit out of it.
I run a Contender 23/25T with a pair of them and we are pushing 2000hrs. They are 2005 motors. The only thing is the lower units are getting loud when shifting.
If it were me I'd go Yamaha for resale, parts/service/warranty, and reliability It may not be the fasted/efficient (it could be i just don't know), but it is damn near bullet proof.
I run a pair of etec 200's on my whaler and have been nothing but happy with them. I wouldnt a different brand engine on my boat. I have only run one suzuki but it was a champ, quiet and smooth. I have run 4 or 5 yamaha's and personally i dont like them at all. they have all been loud going in and out of gear and all of them had horrible low end throttle response. Just my experiences, but the etecs are bad ass engines!
I own 2 etecs, a 225 and a 90. I think the previous statement about half like and half dislike is pretty accurate. The 225 has needed all new injectors and fuel pump that envirude actually jump on to replace. Since then thing have been great.
In the 150 range the Yamaha is supposed to be their best engine. I would lean that route if you need a 150.
the first etecs were junk, i think they have fixed them up pretty good, i have a friend that crabs with a 115 and two years he hasn't taken the cover off yet probably over 2000 hours. that being said i think the 150 yamaha is probably the best ob on the market. stay away from the suzukis, guys here are having trouble stripping out the drive shafts, and rotting out.