Hello, I am 47 years old living in south east queensland starting windsurfing all over again after nearly 20 years off(I know, not too bright).
I am learning on a Bic Nova,short and wide at present but I have an old "Tiga Speed" still in my garage. The question is:- How would this compare (ease of sailing,light to moderate winds) with these new boards ie: Kona, Phantom etc considering the dimensions are very similar. length-340,
width-65,dagger etc.

I can't remember the Tiga Speed much, but I do think that its biggest sister (the Pan Am or World Cup or something) was just about the best polyethylene "raceboard" ever made.

The old 340s etc were designed much more for strong winds than the Kona is. The mast was normally a long way forward of the small and bendy centreboard so they could be uncomfortably out of balance in light winds. This may well become worse with today's sails with their open leach and forward draft.

The Kona has more volume and is stiffer. It is likely to be faster in all conditions and more stable and will balance better in light winds and is likely to balance better in strong winds as well. The Phantom Race 380 would definitely be much faster in all (or just about all) conditions; the 320 (if it still exists) is not the sort of board I like so I won't comment on it.

One modern short longboard I recently tried was the Tabou Windstyler; it was surprisingly good in 10 knots plus but may have been a bit tricky and slow in lighter stuff; I didn't get any steady light winds.