The S and the D are practically identical, and specs note 1200 lbs of ballast, which I know in the case of my S is all water.
Since the 200 lbs sits relatively high (not a few feet below the water line like it would on a regular keel boat), I doubt it's going to make a huge difference in how much the boat heels, but it has got to help some.
200 lbs is not going to affect the performance of the boat much, I think, and if you are not tacking a lot, nimbleness coming out of a turn or during a lift is not likely to be a big factor IMO.
This increases the dry weight from 1650 to 1850, which does not seem to me like it's going to affect towing too badly as long as your vehicle has a decent towing capacity to begin with.
If you get blown over, the 200 lbs will help with the self-righting as long as it stays in place. Would it make the difference between staying afloat or sinking if completely swamped? Probably not, but I don't know just what the tolerances are there, and whether the styrofoam floating between the liner and deck has been removed.
If it were me, I would leave it as long as it looks like it will not shift out of place if the boat gets blown over. PITA to remove, and will probably make the boat at least a tad more comfortable. Apparently the PO decided it was worth the effort.