@Tizkit
Thanks as always for an amazing reply Tizkit. Great insight.
When I was doing some experimenting with the odds calculator it was immediately clear that submarines are the “best” sea unit in terms of best value. But I’ve found that they’re not necessarily the most reliable unit in the grander scheme of things. So taking cost effectiveness and strategic resourcefulness into account I would argue that destroyers are the “best” sea unit because they can block sea zones, hit air units, and defend @2. Not that submarines don’t have their uses, they just tend to be more situational in my experience.
I’d also come to the conclusion that carriers are awesome for expanding strategic possibilities for the fleet. And you’ve actually taught me a few new sneaky tactics I can use them for (never thought of deliberately failing to clear a path for a carrier so that I can suicide planes into high value targets!). The more options you have on your turn the better, and carriers really expand a fleets sphere of influence. But a carrier with 2 fighters is by far the most expensive addition to a fleet, although you don’t have to buy the fighters if you’ve already got a few on the board. Still, destroyers and subs can easily take out a carrier w/ 2 fighters (both unit groups costing 36 IPCs).
Its actually been a tricky question to tackle. But you and @Midnight_Reaper are right. It really depends on the situation and what your goals are. If you haven’t noticed all the conclusions in my videos tend to be “it depends” 
Thanks again so much buddy. If you have any other thoughts feel free to share them!