If your looking for something small, fast, accurate, has anti chop eyes and will take you all the way to tourney ball - get the Ion
If youre looking for a marker to take you from your very first woods days right upto tournaments and you like upgrading progressively then go for the cocker.
My guess is theyre gonna be about the same weight as each other, and about as accurate as each other.
Personally i'd go for the Ion because of the speed and the ACE (Anti-chop eyes)