Depends what you mean by "significantly better".
The 28 only came in masthead rig version. The 30 was done in mhead and fractional - not as many of the latter as far as I am aware. I don't know the sail areas of the two 30 versions compared to the 28 but would guess they might be a bit more. The version above and one which I had was fractional - so longer luff and boom mainsail, and looks like the mast was stepped a bit further fwd for the 30 fractional rig as is usual for a fractional rig due to the bigger mainsail to control the sail area centre of effort point compared to the centre of lateral resistance - even accounting for the extra 2ft on the stern.
sailboatdata.com/sailboat/cavalier-28The fractional rig gives the advantage of being able to sail upwind reasonably well with just the main - most mhead rigs don't sail upwind well with just the main. A fractional rig yacht in the 24-30ft range is so easy to sail single handed with full main and no3 jib. And the walk through transom obviously makes it so easy to get on and off from dinghy.
I would say the 30 fractional sailed better than the mhd 30 and 28 but probably not a lot in it - imho the 30 fractional fastest due to extra waterline and better more tunable rig, 30 mhd next due to extra waterline, then 28.