If we decide on a faster 5 stateroom boat...

Overmarine

Yes I can think of a few instances

Why not buy a 130' Westport to live on and a 63' Pershing that travels with it. Far more versatile. For example you can base the Westport somewhere in the exumas and easily use the Pershing to travel 50NM each way to explore for day trips.

You mean a P62, I suppose?
Great boat and pretty fast, but for speedy day cruises, I'd rather sacrifice interior spaces a bit further and go for an even quicker Otam 58.
Or for much more room, on top of a Fabio Buzzi hull with a record heritage second to none, also an Otam 80.
Anyhow, with the option of a second "toy boat" mostly meant for adrenaline rushes, there's plenty of choices. Also much more extreme, going down in size a bit: some 50 footers like the SV Outerlimits or the Marauder are in a totally different league, in terms of speed...

Personally, I'm more a follower of the principle "two engines, two problems", let alone two boats!
So, if speed is a requirement, I'd rather go for the Pershing 140 (as a best compromise between speed and interior spaces), or the AB 140 as a close second, and call it a day. But that's me.

In any case, the differences between the alternatives that we are debating are so radical, that before talking of brands and models, the OP should make up his mind on the type of boating that he's more interested in, first and foremost.
Jumping in conclusions is never a good idea, with boats...

Hull speed in knots equals 1.34 times the square root of the waterline length in feet (HS = 1.34 x √LWL). I always thought this was the reason for longer & longer yacht hulls. You gain speed ,room & keep fuel flow down.

You're saying spend millions extra at purchase and many thousands extra on every aspect of operation to save a little fuel and run a slightly faster hull speed?

No, just pointing out the fact what hull speed is. I'm with you, 10 knots is to slow for me. Would like 30 to 40 but can live with 20. A longer boat is the way if you can afford silly money. You just keep your 50 foot twine turbine on board for the adrenaline rush .

That's the formula for displacement hulls. The yachts we're talking about here aren't displacement hulls, so the formula doesn't apply. You can always run a planing hull or semi displacement hull slow, like the Westport at 10 or 12 knots and get virtually the same fuel economy as a displacement hull.......(and 9 out of 10 of them generally do travel at 12 knots).

37m Incat Crowther with twin C32's - top speed 25kts and no one will spill a drink in heavy seas. Saw one going thru the CZ a month ago. A very comfortable 5 cabin model, drafting 2m

Yes it does. It runs 48 knots WOT, 40 knots cruise so about 5 knots faster cruise than a 63' Riva. AB's 64 is/was faster. I say is/was as they've removed it from their website, although I'm sure they'd still build one of anything right now. They do have a 787 center console like boat they've added though.

Indeed.
But if you are now oriented towards that combo, you won't regret giving a look also at the Otam 58.
Aside from being even faster, she can also take worse sea conditions in her stride, at any given speed.
The Pershing interiors are better and larger, though.

Then you're looking at HSC or turbine powered trimarans. Outside of this one with twin 1850hp helo engines it doesn't get good until 3:16

12 minutes running the gamut of speed. Ps: Don't assume that what's available now, oars, sails, props and pumps are the only way to move a boat.

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Don't know why this video didn't embed. will edit and try again.

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He also probably sold it because turbines are VERY undriveable around marinas and such.