As others have said, the C26 is an extremely seaworthy design, particularly for a trailer sailor. In a blow you'll need to reef early, but you'll give up before she will.
I have had complete confidence in Windward in all conditions I've sailed her in, which include 4-6 footers (avg... some larger) on the ocean, 3-5 footers in Pamlico Sound (steeep! chop), running the Bogue Inlet, and wind conditions of 25-35 kt steady, with gusts we won't discuss. Even when sailing for several days in waves that left her with air from the keel forward a number of times, she came down with a slam instead off a chuf perhaps 4 times. I raced on a Cal 29 on Lake St Clair for several years, and similar conditions on that boat would loosen fillings.
All other things being equal, a longer boat is usually more seaworthy than a shorter one, but length doesn't tell the whole story, and all other things are seldom equal.
Some of the same qualities that make her heel a bit early give her a seakindly motion for her size and a high angle of vanishing stability (the point at which she's going to keep on going rather than righting herself). If set up properly she's easy to singlehand, but comfy enough for an overnight with a couple of other people. Cockpit's not overly large, but for heavy weather that's a good thing.
For many of us, her sailing characteristics, combined with an enclosed head, actual (if minimal) galley, a vberth with a door and standing headroom make it difficult to justify moving up.
I've not sailed a Mac 25, and the one on our lake is not well outfitted or often used; however, there's no comparison between the boats, except that on a good day both use big white things to make the boat move forward. Construction, design, accommodations, performance, construction quality all go to the Chrysler.
You can look at her vitals vs other boats at
http://image-ination.com/sailcalc.html . The rule of thumb is that you want a low capsize ratio -- below 2.0 is preferable for a boat used in rough conditions. You want a high motion comfort factor.
The C26 has a capsize ratio of 1.87 to the Mac's 2.45; the C26's motion comfort factor is 20.73 to to Mac's 8.8.
Don't know a thing about the SC26 -- if it's the South Coast 26, I do know that its displacement is at least 1000# lighter, which in a boat this size would probably translate to a much livelier motion in a seaway (read: uuuurrrpp!)
Disclaimer, and a disclaimer on it: we all love our Chryslers here, so we are in fact not unimpeachably objective. However, we know our boats' flaws and readily admit to them -- our shades aren't rose-tinted -- it's just that in the balance the C26 in particular is an extremely satisfying boat.
KS