Well, I just did this year and went with the sub-frame and hydraulic angle blade. It uses the FEL controller for the lift and angle of the blade. Works fine, but takes a bit of time to get use to. One thing that worries me is the problem with getting stuck and not having the FEL to help push me out.
As for switching over from one to the other it is rather easy to hook up or take off the plow and can be done in a few minutes. The FEL is a different story and although I have only done it once it took me several minutes to get it off and then back on. This was in nice weather, not too sure how it will be when the temperatures on cold.
I am now faced with going to the dealer to complain about the paint job on the blade. The entire face seems to be pilling off and this is after using it for about an hour plowing snow.
Having a rear snowblower and now a plow blade it certainly improved the time for plowing our road and I am not sure if I will need the FEL or not. I know in years past I would use it from time to time, but really did not need it. Only time it helped me was when I got into a situation and need it to push me backwards.
Just my two cents.