I don't buy the "outboards use less fuel" argument, but I say that with the caveat that I've not run a gas inboard or diesel outboard for a truly fair comparison. Even the 28' whale watching boats running single or twin OBs burn at least twice as much fuel as my 35' with twin I/O diesels. So... from an economy standpoint, my vote is inboards, but be sure they're diesel.
I also don't agree with "all inboard engines are car engines converted for marine use" 100% I don't have any problems getting to filters, starters, alternators, etc. even in my cramped engine compartment. From a service and maintenance do-it-yourself standpoint my vote also goes to diesel inboards.
Under heavy, "mission critical" usage - ie: seatow service, charter, etc. - I can see the great value in outboards... if something semi-major goes wrong, the solution is 4 bolts away with a whole unit on standby. No troubleshooting to determine whether your problem is injectors, rings, drive related, etc... just remove the bad motor, replace with new/spare/rebuilt unit and you're back in business. The "I can't afford a single day of downtime during my charter season" vote definitely goes to outboards.
For a smaller boat, having a raised engine cover (aka: doghouse) sucks with an inboard. MY boat doesn't have such problems, however... twin 230 hp engines under the deck, and I've got 10'x11' of flat, diamond-plate, wide open fishing deck. Except for very specific applications (like a flats boat with a pole platform above the outboard) the outboards are a major PITA to work around when trolling, fighting fish, handling quad-hookups, etc...
I've also decided over the past 3 years that I don't ever want another I/O again... the power loss each time the drive-train takes a 90 degree turn (twice in a typical I/O setting) is horrendous. Gimme a straight-shaft (or at least a v-drive) any day!!! Oh, not to mention the number of moving (aka: susceptible to failure) parts just sucks.
I'm rather interested to see where the evolution of the MEG diesel outboards takes those motors, but I have a strong suspicion my next boat(s) will all have long, straight shafts and engines tucked neatly away below decks.
-Case