Im gonna give this win to Shantae tbh
Winter has an AP advantage of 18.8 tons > 14 , but ofc the gap isnt too big that its decisive, and she can speed amp when it seems necessary, but Shantae's pure versatility wins out here
Maybe if we assumed Winter had everything Weiss could do, it would be fairer, but Shantae has Speed Amp like Winter, and a lot lot more. Winters only real decisive power over her is the Summoning, but shes only ever shown weak grimm and small nevermores.
Shantae has abilities like Invisibility, Transformations (with Size shifting quantities), Flight, Invulnerability, Shield generation, Healing, Magic in general (Something 'godlike' in RWBY), as well as Pike Balls that can prevent Winter from getting close.
Not to mention winter doesn't have the range advantage from what we see, and even if she did, Shantae could reflect/absorb it. She also has access to electricity (which has on multiple occasions shown to bypass aura to a greater extent than other elementals)
Its hard to argue Shantae is more skilled, but we do see a lot more of her in work than we have of Winter.
So yeah, Shantae for all of that, no spite claims please.