Never played either one, wasn't much of a controller guy. It seems like a couple powers share interesting parallels:
Ice Slick and Propel. Ice Slick seems pretty powerful control-wise, but it seems you could slot Propel with the Overwhelming Force IO + Force Feedback IO for a similar if not better effect.
Flash Freeze and Dimension Shift. Both serve the same purpose of holding enemies you don't wish to engage for now. Dimension Shift seems to be better for keeping them mezzed despite teammate interference, while Flash Freeze seems better for mezzing more mobs due to a slightly higher radius (25 vs. 20)
Following that, we have the almost identical parallels in the single target hold, single target immob, and long recharging AoE hold powers.
With the remaining powers, it's clear Gravity gets the advantage in single target damage and control (wormhole) while Ice gets the advantage in recharge and movement debuffs.