Personally, I sail both modern and old-school slalom equipment currently and switching them often.

Examples of modern: ~90L/60cm width modern slalom boards, with carbon fin, double luff camber sails up to 4 cambers from 5.0-7.1
Old-school: Sputnik 270, 280, 290, thommen 285, Copello 275, and have tried an old Gun sail Mega X 6.3, old mistral slalom fin

Impressions on these based on my limited skill:
Boards: Modern board's top speed is very close to the old, or in fact a bit higher. Average speed much faster especially in open water with chop, seems to fly over chop without slowing down as much as old boards. Better upwind for sail ~7m. But once used with sail <6m, difficult to sail downwind especially with the wide tail and outboard footstrap for my poor skill, no problem with the old boards. Gybing similar, occasional planing out for both types. Schlogging, old boards more comfortable if using 10L more than new. In terms of low wind planing, 100L old board equal 90L modern.

Sails: double luff pocket sails are really heavyvery difficult to waterstart for 4 cambers, offen resort to rope pullCentre of Effort very stable, auto-accelerate in gust
Mega X, the only old shool slalom sail I've used, surprisingly light despite 7 cambers. But due to less loose leach, CE starts shifting back when wind up to 20knots. Difficult to sheet in and overpower. Much less high end performance

So I suspect that modern equipment (9m/130L, no experience yet) can be used in lighter wind and by heavier sailors. And once the heavies get going, they are much faster. So naturally, pwa slalom is now dominated by sailors average 200lbs. Is it healthy for the sport to be obsessed with wide board and heavy sailors? Modern sails are so stable that they can be used in mucb higher wind. Again this gives advantage to heavy sailors.

I admit that modern equipment is a large performance enhancement for racing. But a freerider may prefer the feel of narrow boards, which are much nimble and light-footed.
For lightweight myself (135lbs) and only sail recreationally, I don't need wide board and sail much bigger than 7m. Old boards still works, and feels exciting and fast, a bit bouncier.

SongofWind said..
Personally, I sail both modern and old-school slalom equipment currently and switching them often.

Examples of modern: ~90L/60cm width modern slalom boards, with carbon fin, double luff camber sails up to 4 cambers from 5.0-7.1
Old-school: Sputnik 270, 280, 290, thommen 285, Copello 275, and have tried an old Gun sail Mega X 6.3, old mistral slalom fin

Impressions on these based on my limited skill:
Boards: Modern board's top speed is very close to the old, or in fact a bit higher. Average speed much faster especially in open water with chop, seems to fly over chop without slowing down as much as old boards. Better upwind for sail ~7m. But once used with sail <6m, difficult to sail downwind especially with the wide tail and outboard footstrap for my poor skill, no problem with the old boards. Gybing similar, occasional planing out for both types. Schlogging, old boards more comfortable if using 10L more than new. In terms of low wind planing, 100L old board equal 90L modern.

Sails: double luff pocket sails are really heavyvery difficult to waterstart for 4 cambers, offen resort to rope pullCentre of Effort very stable, auto-accelerate in gust
Mega X, the only old shool slalom sail I've used, surprisingly light despite 7 cambers. But due to less loose leach, CE starts shifting back when wind up to 20knots. Difficult to sheet in and overpower. Much less high end performance

So I suspect that modern equipment (9m/130L, no experience yet) can be used in lighter wind and by heavier sailors. And once the heavies get going, they are much faster. So naturally, pwa slalom is now dominated by sailors average 200lbs. Is it healthy for the sport to be obsessed with wide board and heavy sailors? Modern sails are so stable that they can be used in mucb higher wind. Again this gives advantage to heavy sailors.

I admit that modern equipment is a large performance enhancement for racing. But a freerider may prefer the feel of narrow boards, which are much nimble and light-footed.
For lightweight myself (135lbs) and only sail recreationally, I don't need wide board and sail much bigger than 7m. Old boards still works, and feels exciting and fast, a bit bouncier.

Forget it! Twenty years old slalom boards were bloody scary. Out of control Broncos. By about 10-12 years ago things really got better: boards were faster, safer AND easier. Then, in my opinion, things started to diverge a bit. While larger slalom boards got easier and easier to ride (an Isonic 107 is marvel compared to any old 72cm wide board), slalom race boards in general got a bit more technical. Example: My Patrik 100 Slalom is a more technical board to ride than an Exocet Slalom 2009 I recently inherited.

But still ... I would not go back to any of the boards you list for any reason. Size? it depends on body type ... I am small and I am very happy with a 90-100 liter slalom in 6.0/6.6 maxed out conditions, anything bigger than that I can get not too happy fast, especially in chop, if conditions freshen up above a certain limit!