Very well said. In the original conception of the sport, when it was booming, the "funboard" was the workhorse and a shortboard was something you considered unpacking when it was 20 knots and over.
Now some newbies buy their 130 ltr/6.5 and bob around in a gusty inland 8 knots, expecting to plane.
I started out on a longboard and in light winds, little can compare. Even the best raceboard pales in comparison to the Windsurfer OD's upwind angle in 5 knots. Then again, you can paddle a SUP or kayak faster upwind in that wind. It's all very finicky obsessive/compulsive stuff that rewards a minority of hardcore light wind sailors ( a crowd who's champions often get pared down to the 140 lb triathletes and anorexic asians
Now, if a typical north american windsurfer invests that same energy into packing the car and choosing a coastal/ great lakes, river destination on a steady 15-knots and over day, you'll see greater return from a standard shortboard quiver than any uber-expensive custom raceboard setup. You;ll get stronger and more...um, "rough n ready" with a dozen good shortboard seshes than a whole season of lightwind longboard. A new raceboard is redonkulous cash. A used longboard likely has neon pink footstraps, and is made by a derelict company with a three letter acronym for a name, you choose! A used formula is less onerous, even if it's breaky. And chix diggit, think of the money you'll save in bars.
Yes longboards have great glide, upwind railing and "carry" when they're up and planing, but the jibing is inherently chunky. Planing through is a pro level thing, the radius is fixed. Shortboards have gotten very refined and have power in jibes and you can really lock in and experience true acceleration and airtime. It's a function of having less mass.
And wide shortboards are more predictable and easier to balance on. A lower center of buoyancy, usually below the waterline, is actually easier to slog around on than a high volume longboard, which can be like standing on a log, even though slogging a shortboard is tiring and boring, and a longboard in those same conditions is graceful and responsive.
Want to know what the kids are doing these days? They're buying freestyle boards and going out on 5.4's in 9 knots just to slog around and light wind freestyle, ie helitack waterstart, gecko, falling in. Boring to watch but it's useful practice. They're buying 18m Foil Kites and cruising in 5 knots, no questions asked. What they're not doing is worrying about a board's waterline length or weather or not a 11.5m Vapor is going to pull you in 7.99 knots. They're also not debating on anonymous internet forums or faxing intimidating letters to Windsport like highwind Steve from Maui who thinks longboards are for grandmas or lightwind Dave who thinks anyone who owns a 80 ltr board must be a six figure alpha elitist who owns half of Hood River. If the wind isn't there, there are other things to do that will give you a workout, bikes, skate, snow, surf. Slogging around on a 99l is tedious, but when the wind comes, they'll be ready.