A tiller is nice for smaller plots, less than an acre. For anything one acre or larger, a disc is the way to go IMO. Much faster. You mention rocks, stumps.. Disc is also more desirable here.
If you get a true box frame disc, the gangs will be adjustable and you can straighten them after you disc to break up the clumps and better prepare the seedbed. (FYI - An angle frame is a lot lighter.. A cute toy but doesn't do much to disc the soil).
Box Frame Disc below. Heavier, more versatile..
View attachment 38125
Result looks like this, after straightening:
View attachment 38124
Lastly, if you go with a disc - Don't get anything wider than 6' for that tractor. The issue isn't power, but rather weight on a compact tractor. Even in MFWD, if you don't have Ag tires you won't be able to use that power. Utility tractor = Different story..