Ok, fine.
336mph at sea level (Spit XIV does 358)
405mph at 20,000ft, IIRC (Spit XIV does 448mph at 27,000ft)
Initial climb somewhere between 4000 and 4500 feet per minute (about the same for the Spit XIV)
Higher roll rate due to the clipped wings. Slightly worse at turning due to the clipped wings.
Basically it is a better rolling and accelerating, slightly faster on the deck Spitfire Mk IX.