first off.... you want an 820... lets look at why. Start with the input, stronger steel cut gears and larger 3/4"input on the 820, compared to the 5/8" input and sintered (cast) gears on the 200 series. it weighs almost 20 lbs more according to shipping weight on several sites. the 820 is the dirty one, that makes the 200 the shiny one obviously.
Below, you can see a close up of the 200's 3/4" axle, compared to the 1" on the 820, you can also see the beefier mounting area, and more reinforcing area built into the casing.
here you can see the amount of space used on the casing, for gears and internals, its quite a bit more in the 820, you can also see the difference in the axle drive gear, a weak point on the 200, as it isn't nearly as robust.
the 820 is designed for "Ground engaging devices" such as plows and etc used with garden tractors, as the 200 is designed for smaller riding mowers(such as the 16 hp small frame/small tire bolens/mtd/etc)
the 200 so far has held up acceptably within riding of my ATGC, I would point out it WILL NOT handle recovery, high resistance towing (mud or muck) wheelspin in high traction situations while vehicle is not moving. if you run it thinking its heavy duty you will eventually blow a rear gear tooth through the casing, and it will not move again, (though the brake output does continue to spin, using that as an output might be better/stronger)
you can tell the difference in the retail price of these transaxles as well, the MST 200 is findable on "surplus" or "overrun" sites for around $75+shipping new (retail is around $200+/-), the 820 retailing around $400-600 depending on the model, and it is very rare to find on "surplus" or "overrun" purchase sites, and when I have seen it, its around $250.
I found the 820 in the pic for $75 at a lawn mower junkyard, he had alot of neat stuff there, including a (in need of restoring) john deer 110 from the 60's, a few simplicitys, wheel horses, and LOTS of other stuff. I had taken the 200 with the gears on it with me to show him what it was for, he said, "thats a toy compared to the one your getting" and from the specs from peerless, hes right.
http://www.tecumsehpower.com/Products/Commercial/pdf/200.pdfhttp://www.tecumsehpower.com/Products/Commercial/pdf/820.pdfthese are from -
http://www.tecumsehpower.com/Products/Commercial/index.php
