The only reason why Sora is above Ven is because Sora also has Ven's heart, which gives him Ven's powers/strengths as well.
Without that advantage, I'd say their dead even.
Sora is still prob stronger than Ven physically but Ven has the stronger magics and Ars Arcanum.
Terra is the strongest physically, Ven has the strongest magics.
I don't remember a transfer of hearts ever granting any extra powers in Kingdom Hearts. As far as I know it grants memories and from that the knowledge of certain powers, but if it requires something more than just knowledge Sora is screwed.
Sora is still > via power scaling.
Then there's all the crap nobody seemed to disagree with in Sora vs Link. Those include his drive forms.