Grip Line versus RGL; Confessions of a Spike Addict
Grip Line: High shoulder and somewhat domey (unless you have the money snot green ones). Great off the tee but unable to take much snap because they aren't very HSS and their LSS doesn't really kick in unless you throw super nose up. Great glide, great distance potential, great feel. Highest weight I have owned in Grip was 174. Probably the one plastic that any company has cancelled that they shouldn't have.
RGL Spike: Varying degrees of dome (seems to be color AND weight related). Mine all have high shoulders but are pancake flat on top (all of mine are 177). Definitely more HSS and LSS then the comparable weight Grips. Seems a little gummier, a little slicker and a little more durable. Glide has not been compromised from the change in plastics. Not OOP. Prettier then any Grip I've ever seen.
End Result: If you are looking for an easy to find replacement for a Grip Line version, they are money. If you've never owned a Grip Line and just want an awesome neutral driving putter, they are money. If you are sitting on a stack of Grip Lines, the only reason to pick them up is to make it less painful when you lose them on a drive (easier to find for sure). Cannot go wrong with a premium plastic Spike :-)