Re: Hydrofoil
For the dollar, nothing will get you on plane faster than a hydrofoil on the leg. Trim tabs and hydrofoils both lift the stern from behind the transom and get you on plane faster while also allowing you to operate on plane at a lower speed. Both give you more control of speed before you get on plane.
The hydrofoil lifts on the leg so you add load to your steering from the force of that lift. For many boats it can be a quick fix to make the boat better for how you use it. Other negatives can include increased spray at the transom. Don't expect the foil to stop porpoising.
Jdeagro is right that the lift increases with speed which is usually not what you want. This means that any increase in steering stiffness is higher at top speed, although you may not notice it at slower speeds. You do compensate for the lift when you trim up the bow at high speed. You are dragging the foil through the water at top speed but you have also lifted more of the hull out of the water so you probably won't see much sped loss.
Trim tabs have other benefits that a foil cannot help with. The compensate for list when you have a hull that does that naturally or when the boat is loaded unevenly. They can also effectively work to reduce porpoising and with helm adjustable tabs you have a second way to control the attitude of the boat in a storm or in rough water.
A foil like the Stingray probably gives the most lift. One like the Doel probably affects the handling the least. For wake boarding a foil works better than tabs.
For me (who has a foil on one of my boats), my first choice would be helm adjustable tabs, then Smart Tabs, then a foil. Please note that is also the order for price from high to low. Pick your budget. You get what you pay for.
