They both do basically the same thing except the discharge of 30 on the checkpoint is pulsed and not linear - take a little longer to discharge a full pack but.. along with some other features.
I personally gave up my gfx for a duratrax ice which is what the checkpoint is based off with the backlighting and a couple updated items.
I would get a checkpoint based on the price, size and the functions.
You wont go wrong with either but with the checkpoint you would have a little $$$ left over to buy other parts or batteries. Heck I think you could buy 2 of them for the price of a new GFX.
I plan on picking a checkpoint up here shortly.