This only partially relates to the discussion at hand but I think we've got some misconceptions about powershielding. Powershielding a laser isn't a punish. It's a conduit through which you can turn certain kinds of lasers into an opening, similar to jumping over lasers, wavelanding off a platform over them, dashing under them, or crouching > movement under them (and so forth). For a lot of characters (probably most of them but I've never looked at it too seriously), successfully PSing a laser is a stronger option than the other main methods of working around a laser (jump, jump > platform waveland, traditional shield > WD / jump OOS) because the stun of the laser plus the faster movement (jump is slower for most characters than WD for covering distance) giving a larger window to punish. It's also, all things considered, a fairly low commitment option from a distance if you simply don't want to go through the effort of repositioning around them (which is also a big part of it).
What matters for a powershielder is how quickly they can reach Falco after PSing a laser and from how far (and also what they can do to Falco, I guess, but everyone has throw > death on Falco so whatever). Mario's powershield game will never give him an even MU (or favourable one) with Falco because even with the powershield, he's still got no range so the windows are still tiny and he needs very specific distances. For characters like Sheik and Marth? This is not so much of an issue.
edit:
Blistering Speed - Peach's shield game, zoning, and low variance in her combos probably could be argued to secure her a spot among the top characters. She's also more resistant to death than most of the other top characters in that her recovery not only exists but comes with low lag options.
Peach probably has the best shield in the game with what she can do out of it and how she gets hurt somewhat less by grabs than the other characters with shield options (spacies and Sheik).
