I made up the term "speed floor" years ago as "the point at which you turn on the engines if you go any slower". I don't think it has anything to do with "type" of sailboat. It's a variable that will change moment to moment based on a lot of factors: I think planning speed AND speed floor are likely to be higher on any boat that's capable of going faster, so "speed floor" tends to be higher on a higher performing boat regardless of how many hulls it has. Primarily it's about patience. You mentioned motion, but going slow the speed floor is not at all about motion (the only time motion is a factor for us is in a big chop, such as strong wind-against-current when we might slow down deliberately).

First of all, the context in this thread was that Gene used the term "planning speed". That implies the boat is on a passage, not a daysail. There is never a planning speed on a daysail, when we're there just to be there, and whichever way the wind blows we'll likely choose a course that let's us reach. 2-3 knots is just fine under that circumstance, but faster is always more fun. Below 2 knots we're really just drifting.

When going from one place to another the concept of "planning speed" is subjective. It is a sailboat, with all the variables that go with sailing. The "speed floor" is the point at which you will turn on the engines if you go slower. For many people the speed floor rises as your cruising speed under power increases.

For us; our boat cruises at about 7.5-8k under power so on a passage our speed floor under sail is about 4 or 5, or might be even higher if we're trying to make port on a schedule to beat darkness or weather. With a favorable wind we can sail in "the teens", but because we can't count on that our "planning speed" is 5 or 6 knots. We prefer to sail when we can. If planning for 6 but we're sailing at 9+ we might decide to press on to a more distant port or just arrive early and enjoy the destination with a little more daylight left.

IMHO - Keeping planning speed slow provides a better mindset for crew to enjoy the journey in a sailboat. It takes the pressure off and lets you sail more.