BY FAR.
Are there any drawbacks to the mid length gas system?
From what I had read online it appears that they are really great. The only downside I could even think of is that with the midlength, your forced to use longer hanguards to cover up the extra gas tube, which adds more weight.
Is this the only drawback? I don’t have any experience with them, but would be interested to learn of the pros and cons of the system.
I’m a big fan of middies…
Longer part life, more real estate on the rail - I find carbine handguard very short.
And of course the most important aesthetically pleasing 
In fairness though, it is possible to very easily “fake” a mid-length by just putting a longer handguard over a carbine-length gas block.
I think the part life and possible affect on recoil being the only real value.
I’m with Kevin on this one. I’m tall and hold the handguard near the end. The couple extra inches makes a big difference. Plus on a 16" gun you get a more balanced look. 16" carbine guns look almost goofy long on barrel to me. And like Rob mentioned, the recoil tends to not feel as sharp to me.
I would take Middy Colt over Carbine by Colt
I have long monkey arms as well, the middy length free floats are perfect for where I put my foregrip and light.
Personally, I’d take a 20" over a 16" carbine upper, as long as I had a telestock on it. Tried one for a while, it shot great and was reliable, but it just bothered me knowing I could do a little better (especially since I usually shoot with a can).
I believe Grant is getting Noveske 16" middy 1/7 chrome-lined stainless barrels. Couple that with a LMT upper and you’d have a awesome middy.