The PA4 is a straight to slightly understable putter. The PA4 has a tall profile and blunt nose and very ergonomic grip. The PA4 will turn up when thrown hard and will then have a long glide and gentle turning finish.
The 400G series is the regular 400 plastic with a shot of adrenaline. It is the base 400 plastic mixed with another resin that give the plastic a slightly different feel than the base 400 series. The additive also makes the disc more durable and requires more time to break it in.