I've owned two Searunners, a 25' and later a 31'er, and I've been interested in Horstmans going way back as well. I've worked on both, sailed both, and have a background which includes some yacht design, engineering, etc. Ed Horstman and I communicated a lot years back and I once met his better half when they lived in the LA area.
Both have enviable records of both
safety, seaworthiness, and make excellent coastal & long distance cruisers. But they each their idiosyncracies.
Searunners all had/have center cockpits. Very safe place to
sale from, good visibility all around, but it chops up the
interior plan a lot. The 31 is really too small for a
family, but the 37 was exceptionally good for distance cruising.
Storage very good for stores, water, and
engine placement is below the
cockpit. The large centerboard makes for very good windward ability as well, plus very
shallow draft if you intend to beach the tri.
Hortsman TriStar tris all use daggerboards, one per AMA (outer hull). These are as good or better than centerboards for windward
work, but have one potential weakness... if you ground out or hit something with a board it won't ever pop up as the Searunner CB might, if rigged to do so. It would take a heck of a THUMP to pop a secured CB, and might do more damage than to just the board, perhaps coming close to what a daggerboard might do if it get's hit hard enough to break... possibly bust the DG box a bit. However, both possibilitites are small.
I've sailed a 27-9 with at least 6 adults on it, waiting in knee deep water for the owners son to come aboard,
mainsail only, no boards, and it tacked easily. Once aboard, it sailed with main &
jib wonderfully... and a modern racer/cruiser
monohull at least 34' long with larger
sails didn't catch us!
Both designs and their adherents, and you can read the literature. Brown was self taught, Horstman was an aeronautical
engineer and applied his background to tri design.
My own preference leans towards the Horstman tris, especially after owning two Searunners. I think the Tristar designs are better for
living aboard for one. The Searunners are great for cruising, but are rather "clunky" in terms of
living aboard due to the centerboard &
cockpit between foreward & aft cabins. Otherwise, aesthetics are largely personal, and the TriStars, up close & personal, can be pretty sleek looking with a good
paint scheme. But they can also look boxy, it depends on what's done with them. Searunners allways look like more conventional designs with somewhat boxy cabintops.
I'll just mention that having met and discussed design with the late Norm Cross, and admiring his designs, I still found them not as good for living aboard as the Horstmans, plus Cross designs all have a fin
keel which precludes laying upright should you beach the tri. While fin keels
work well as lateral resistance & getting
lift to windward, they are not necessary and frankly, to my thinking, eliminate one of the major pluses of most multihulls... having the ability to use very shallow water when you want, to beach the
boat & even
live aboard nicely while beached, yet still go to windward as well as anything, all without the hindrance of a fixed fin or long deepish
keel.
Remember too what fast tri
designer Dick Newick said about having a boat with low cost, high speed, &/or large accomodation: Pick TWO, you can't have all three.
Hope this long post helps!