Yo MC of "da" Mack:
4416= good box and good sound, very good sound.
2816= all of the above but not as many faders.
AW16=another spin-off product and also shares the fine sound of both of the above but with some differences which may or may not matter to the average dude who records.
4416 is probably a bit tougher to learn.
2816 is not easy to learn but it depends on past experience or computer savvy.
AW16 = can't comment on its learning curve as I've never touched one.
One advertising point of the 2816 was that it was easier to learn than the 4416. Reason for 4416's lower price is that some early units lack what is in the 2816 but Yamaha quickly put in downloads.
Sound quality of all units=very very good. Depends if you like 16 faders or 8 faders that do sixteen tracks. For me, I seldom do more than 8 tracks so the 2816 if fine. But, if I had bought the 4416, I'd probably say the same thing.
You will need a USP power supply unit with whatever unit. It's in the manual for the 2816 and I assume for the 4416 that if you lose power while recording, you can lose your data and screw up the hard drive. My USP unit was not expensive but I did not know up front that I needed it. Also, make sure you check out shut down procedure. You just CAN'T flip the off switch -- you have to shut it down like the computer it is. Love the built-in CDRW burner too.
Green Hornet 
