Tiller - 128 - 1450
1) Don't worry about a creeper gear on a plow tractor. You won't use the creeper reduction to plow and I have never heard of someone tearing one out while plowing in "direct drive".
2) Hyd. lift is NICE for the tiller!!!!!
3) The hydro on your 1450 will need to have a nice "tight" linkage to make accurate tilling possible without big surges.
4) The creeper will provide constant and smooth speed while tilling.
I personally would probably put it on the 1450, especially if your 128 is your plow tractor, if only to save you taking the gear box on and off before every plow day.