It's a balance. Better control and accuracy with shorter leaders. Tighter loops too, so less snagging on overhead stuff, and you can squeeze casts in tighter places.
The drawbacks are getting a drag free drift is harder, and getting deep is also harder. So I tend to think of it as big stream dry flies or deep nymphing favors long. Tight brush or shallow nymphing favors short.
I tie my own leaders and honestly, if I got my heart in it, may adjust my leader dozens of times per day. Tricky currents and can't get the right drift? Or really deep spot and gotta get it down? Lengthen it. Gotta tuck one under that branch and get it right against the bank? Shorten it up. More often I'm lazy and go with a shortish taper, but then add or subtract tippet length as needed. Same effect, but you sometimes end up with a short taper and long tippet, which is less than ideal.
Frankly it's pretty rare that I'm over 10 feet total, so I guess I'm mainly in the "short" camp. Maybe midging in frog water, but I tend to avoid that. For the most part I'm somewhere between 6 and 10 feet for leader plus tippet. Typical for me would be a 5 or 6 foot main taper and then constantly adjusting between 1 and 4 feet of tippet. A brookie leader may be more like a 4 ft taper and then 1 to 4 ft of tippet.
You can also play with stiffness of leader materials, and there's a whole world out there with furled leaders, flat leaders, dropper configurations, etc. Learn to cast first, this is probably too deep for you to dive into at the moment. But as you advance, learning leader adjustments to do what you need at the moment are probably more important than fly choice and all the other stuff we tend to focus too much on. For the time being start short, get on target, and then lengthen as refusals, rather than accuracy begins to become your main problem.