Shamrock is better in the ring, but Roddy Piper is certainly smarter. Piper made a career out of beating guy slike Flair and Hogan routinely, despite having a moveset that consisted of punch, eye gouge, and sleeper. Yes that's right, Piper has the 3 moves of doom. Despite these limitations, Piper managed to be a big name in the business for damn near a decade, and st ill gets damn good nostalgia pops to this day.
Yes Shamrock is tougher, yes shamrock will probably out brawl Piper, yes shamrock would is more technical. However, does anyone ever remember Roddy Piper tapping out. Shamrock would have to break that ankle before Piper submitted. Plus, Piper is smarter then Shamrock. Shamrock became a walking joke with his "snapping" in matches, and getting himself dq'd. So you couple the fact that pipers IQ and Shamrock's apparent lack of said IQ, Piper does something that causes Shamrock to snap and get himself Dq'd.