im a boat guy, ive worked in boat yards and built boats my entire working life.
the ultimate decision is up to the person wanting to buy the boat. but here is some semi professional advice and facts. after owning a 140 merc outboard, countless hondas and finally a 190hp inboard, i have to say i like the inboard best, but thats becuse its what i know most about.
OUTBOARDS:
outboards usually have better resale value for the boat if the engine takes a crap. its alot easier to sell a boat that just needs an engine put on the back of it vs a boat with no outdrive or a fried inboard. if the next guy wants to put his engine/drive in the boat, he now has to glass up the transom to re-drill and re-cut the holes to match his unit. a boat without an inboard/outdrive wont float... a boat without an outboard will.
the outboards that get stolen the most are under 30 horsepower, thieves are lazy, some love 6-15hp engines for blasting up sand for geoducks (we all know who harvests geoducks)
lighter, and tend to be better on fuel.
while inboards are easier to work on, on a consumer level, outboards can simplify whats in the boat, less wires and hoses and stuff
honda hands down is the best small boat engine available
if you dont like the outboard, want something bigger and faster or perhaps smaller and more economical, it is a hell of alot easier to swap an outboard than it is an I/O.
the tolerances on an outboard are alot smaller than that of a sterndrive. example: you are in the shallows and suck up some sand, on an outboard chances are thats going to plug up your entire engine, whereas a sterndrive has a better chance of passing debris through the engine. however if you hit something on an outboard, like a deadhead or something, the dammage wont be nearly as bad as an outdrive
if you are a do-it-yourselfer, GOOD LUCK, they can be pain in the ass to work on
I/O, Sterndrive, aka Inboard
ALOT cheaper and easier to work on, if you arent familiar with boat engines, an I/O is similar to a car engine, its right there. average joe can fix an inboard, where as an outboard is more specialized
there are more parts on an inboard, so if the boat is going to be kept in the water, there are way more things to keep an eye on such as bellows and exhaust boots. if those rubbers go out, the boat goes down. but nothing that proper maintaince wont prevent
the deckspace can be slightly minimized with an inboard, and visa versa with an outboard. if the boat has a large engine well, that protrudes almost 3 feet forward x the width of the boat, well thats 3 feet less deckspace vs a doghouse (inboard cover) that is 3 feet x 3 feet that just takes up some space. for example my glasply has more deckspace with an inboard than the outboard model does.
i favor an inboard because of the aftermarket features. if i need more electrical power, i go to napa and get a bigger altenator. that enables me to run my fish finder, radar, 2 radios, my heater, downriggers and wipers all day long with out putting any strain on the battery
inboards can be crammed so tight into a boat however, that it is so frustrating and almost impossible to work on however. not all are like that, but if the boat you are shopping for is... go outboard
a 4 banger inboard will probably get the same fuel economy as an outboard.
if you suck up a downrigger cable or a line in an outdrive, well, have fun swimming... even if you raise your drive all the way up, you still arent going to get it out of the water vs an outboard, well that will rise alot higher, so you might still have to jump in, but you wont have to dive. but more than likely with an outboard you can hang over the edge with the wheel turned hard over to one side and have your buddy hold onto you as you untangle your gear
those are just a few things ive learned mostly from experiance over the years. just passin on info
happy boat hunting!!! see ya out there.