Re: another "which one is better for us?" thread: H25, Catalina 25, S2 28...
'87 Catalina 25 is near the end of a production run and has the nicest set of details of the Catalina 25's made. If it is in good condition then $5k is a very reasonable price. I had a tall mast 1984 Catalina 25 and it sailed very nicely and was a great boat to learn on. It was forgiving, performed reasonably well, and was comfortable for weekend trips.
S2 boats generally have a higher quality construction than Catalina and a 28' boat has a lot more room than a 25 (especially a somewhat narrow 25 like the C-25). So that would make giving the S2 a good look worthwhile as well. At boat that length should have an inboard and that is going to increase maintenance costs and complexity (but has the benefits of better fuel economy, quieter running, and the prop doesn't come out of the water when going over big waves).
I would suggest getting a proper survey on the S2, where if you are mechanically inclined you could probably survey the C-25 yourself after reading the Don Casey book. If the S2 has an inboard pay close attention to the condition of the current one, $5k boats with inboards usually have motor issues and replacement is at least $10k.
I recently sold my Catalina 25 and went to a Pearson 28-2 (a little bigger than the S2 that you are looking at). The Pearson has a lot more space which will be nice for cruising and it sails a little bit better (faster, points better). However the Catalina 25 was much cheaper to maintain. It's hard to beat the simplicity of an transom mounted tiller rudder, outboard engine, and a mast that is designed to be dropped without a crane. My P28-2 is hauled out right now for bottom paint and other maintenance and the bill (with me doing most of the non-paint work myself) is going to be close to the purchase prices that you are looking at. In contrast a friend just hauled his small Catalina for bottom paint and was done for under $1k without doing any work himself.
If you don't need the interior space of a 28' fit boat then I'd stay smaller.