The best designs are "one off" custom built boats, although there are a few good production cats out there.
Build quality is important, but will NOT make up for a bad design. Most new cats were designed to resemble an apartment, & thus, sell boats!
The boat needs to be built very strong, but also light weight! It needs to be "sailed light" as well. (Leave the fine
china at home)
In a 45' boat, you need enough wing clearance to drive your dink through, and "just barely" standing
headroom in the bridge
cabin.
You need a smallish
cabin, with good walkways forward, and lots of open netted space between the hulls forward.
You need a shaded
helm, with good 360 degree visibility. (And a high clew headsail that doesn't block your view)
Smaller cabins are for a low COG and less windage, so are better, as are smaller cabin side
ports, but really good ventilation.
You need protected rudders that are either "kick up" or RUGGEDLY skeg mounted, and not as deep as the mini keels.
If it has boards, centerboards, (with internal rubber bumpers and a fuse line to hold it down), are FAR more forgiving to impact that daggerboards!
You want all heavy payload (engine /
batteries, tools, tankage,
scuba tanks)... as low in the boat as practical, and as centralized as possible.
Ground tackle, (chain & windlass), need to be far aft of the bow, on the forward cabin's wing.
You need a rig &
sails that are balanced, not over canvassed, and really easy and quick to reef or strike.
Remember... Many of the things that catch your eye at a
boat show, and make you think: "WOW, this is palatial"... Are the very things you DO NOT want, IF you want a good, solid,
SEAWORTHY,
multihull.
The pictured cat was designed & built by my friends Jeff & Jose Allen. It fills most of these requirements well. They found this boat to be "more boat than they needed" in
retirement, and are currently cruising the
South Pacific in their Cross
trimaran, after weathering a
hurricane at sea!