it was my understanding that the "new" 20hp yamaha is efi. Exactly the same engine as a 25, they just pulled 5hp out of it.
still heavy for a 20, however. In my opinion.
My dad has a 20hp carb, brand new 2014 model (bought used from the original purchaser). Love it. The carb setup works excellent; as good as efi. Runs almost identical to my 25, just a couple less mph. Sweet little motor!
tohatsu/merc (same motor) is a little on the weak side at lower speeds, or it felt that way to me. Could have been simply the rig it was mounted to, as I know nothing about that particular hull. Sure didn't impress me, aside from being easier to tilt (but not by much). It IS light, but look how they cut weight....lots of corners cut, it felt and looked a little cheesy. Little bit on the noisy side too in comparison to dad's F20. But it is cheaper, for a lot of reasons. Don't get me wrong, I'd own one, if I needed one, but would certainly rather own a yamaha, you just hardly ever see a used yamaha on the market. Come to think of it, not common to see a tohatsu on the used market either.
some guys hate the carburetor, others hate efi. I don't care either way as long as it starts/runs. Carb is a little easier to work on when/if the fuel gets old. efi, if you plug an injector or fuel pump, you're gonna spend a lot more money. It's a good practice to keep the fuel new, and keep in mind that the fuel also sits in the motor, so it's good to run it once in a while. Even if it's on the muffs or in a barrel.
when I said noisy, at around 1600-2400 rpm I can hear the lower unit gears "whining" a little, and the whine runs up the leg, I heard it pretty good. Also could hear the air intake and exhaust a little (combined). If I were trolling at, say 2000 RPM, I'd certainly be unhappy about the noise. Dad's is pretty close to silent. Actually this past week on the river, had a could other boats pass me going back to the dock really early, and could not hear them coming, both F15hp yamaha (which is identical to the carb F20).