Everything is reliable if you maintain it. Some people like outboards, and some I/O. There's pro's and con's to both.
Personally, I like I/O. The engine is based on automotive (car) engines and parts can be easier (and sometimes cheaper) to acquire. The Alpha one stern drive is a well proven unit and services power up to 300 HP with no trouble. Also, I just like my engine under a hatch where I can have some room to muck about.
Outboards, being more compact (and everything fitting inside a case) are sometimes more difficult to work on. Parts are specific and can be pricey (as can anything marine related). Some say outboards are easier to winterize, and smaller ones can even be brought into your basement for the winter
. Also, should you change boats and want to keep your power unit... no problem! Then you have the 2-stroke, 4-stroke issue to deal with. (Hint: go with a newer 4-stroke)
So, it really comes down to your preference. Those ugly lumps bolted on the back of your boat with cables, hoses and lines running all over, little pieces designed to fit in a crack where you can never get your fingers or have to disassemble half the engine to get to... or a smooth, sleek silhouette of your favorite hull with nothing to spoil the view and an engine room to keep everything out of sight.
Your choice