Pretty much in the same situation as you there Sparkey, went and talked to Secret Spot shop in Scarborough about moving from rentals and buying my own but wanted a board to progress on- ive surfed an NSP board at a surf school and loved it as it was so reliable for going down the line but was a killer to try and turn and lost speed alot.
They recommended the 7s Superfish XL (id had my eye on it for ages) and read ace reviews, a big selling point was the ability to move my back foot gradually further back as i got better and create sharper turns and possibly some cutbacks . Whilst they said the NSP was great for learning and couldnt be faulted for beginners the Superfish was a board that would progress with me- effectively making it a longer lasting board as i wouldnt get bored of it once i mastered standing in my learning stance. Its also meant to be a fast and reliable wave catcher that will increase my wave count without being samey .
Also, the Superfish maintains its price if its looked after and they offered a good part ex price if i did want to move to a shorter board in the future.
Im taking the Superfish out soon and will post how i get on- if i were you id go in and chat to your local shop/shaper and ask as many questions in person- get them to talk you through all aspects of the board as it really settled my mind for spending shed loads of money i shouldnt!