Hi,

if the supply is noisier than the ground, I think your better of with a PMOS (biasing) current source on top of the
cross-coupled pair. You can understand this by considering the 'limit' case where the PMOS current source acts as an ideal (SPICE) current source:
not disturbances coming from the supply can now enter your tank anymore!

Make sure to keep in mind the noise/PSRR of your VCO control voltage too!

Kind Regards

Peter