One's a simple - if space-hogging - system, and the other is a
compromise.

An inboard engine is generally heavier and less compact than an
outboard engine of comparable horsepower (HP). Its size and power are
not limited by a need to have everything in one unit. The engine is
placed near the center of the hull, very close to the lowest point,
creating a low center of gravity. This is a very good thing! On the
back of the engine is a transmission (gear box), which is attached to a
propeller shaft. The shaft passes through the bottom of the boat and is
supported by one or more struts, located on the bottom of the hull.
Attached to the end of the shaft is the propeller. A rudder, placed
just aft of the propeller, controls the direction of the boat.
Some advantages of an inboard a

The engine is positioned to give the boat better balance fore and aft,
and create a low center of gravity.
Although open to some debate, the straight inboard system is generally
considered the simplest and most efficient method of transferring
torque (power) from the engine to the propeller.
Some of the disadvantages are the inboard system takes up a lot of
space inside the hull and, because the propeller is in a fixed
position, the inboard is not as maneuverable at a low speed or while in
reverse.

The Vee drive is a variation of the inboard system. This system is
sometimes called an Angle drive. In this configuration, the engine is
installed over the propeller and rudder, with the drive shaft facing
forward instead of aft. The shaft then enters another gearbox that
changes its direction by 180=BA, sending the propeller shaft back
through the hull to the propeller under the engine.

The main advantage of the Vee drive is that it places everything in the
stern of the boat, leaving much more interior space for cabins, etc.

A main disadvantage is that the entire weight of the engine and
propulsion gear is located at the very stern of the boat (that old
balance thing again). Another drawback is that, by passing through a
change of direction gearbox, you are losing some efficiency and
increasing your chances of a problem with the drive system

Best regards
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