You might get many saying they are very different, brands.
IMO they are REALLY matured now, so brands offer many different sizes and types yes, but there are not really many "dogs" anymore, like the early years.
You will still be positively or negatively surprised when you try something different, yes, but you could also do that within the same brand.
One thing that stroke me: You wrote you use a 1250 Naish wing (area in cm2?), so assume you are average weight 75-80 kg as you didnt write your weight.
And you write "Next step" - which I dont understand.
As today, if you are into freeride carving and transitions and a bit of wave fun, you dont need a "beginner" foil and then another one later.
The smaller wing will be worse at everything above.
BUT, if you like to go fast, or ride long trips, and like to jump, then you need a smaller wing.
Market is so matured today, so there are hardly any too thick and slow beginner wings which should be changed when experienced
But most will change to their own preferred style, getting the wing and board that suits - and they have no idea till exerienced, where their "target" really is.
I cant see you are being off now though, without knowing you