The Cat 250 looks to be a Mac 26 (original, not X or M) competitor, not a high tech racer
The water ballast allows you to get your boat up and down a ramp
a lot more easily due to lower weight and shallow draft
(1' 8"), allows for a smaller car for towing, and allows for very shallow gunkholing or sailing in shallow areas.
On the other hand, lead is 11 times denser than water and is in the keel
under the boat as opposed to the water ballasted version where the ballast is in the hull
I've not sailed either the original Mac 26 or the Catalina centerboard
boats. I have been interested in trying one out though. So without having actually sailed one, I would say if keeping the boat on a trailer and typically going sailing on nice days (defined as lower wind) is the priority, then centerboard
. If you're more interested in higher wind
and better windward performance then keel
Bill Lee wasn't impressed with the centerboard version's sailing characteristics.
Cruising World - Catalina 250