I've seen Fantasmic at
Disneyland, so I'm just wondering if the Fantasmic show at WDW is the same. If they're different, which one is better?
Better is in the eye (or other body parts) of the beholder. (And to this beholder, it's Disneyland coming in first.)
Several aspects of the shows are different.
DLR-
•They use the REAL Pirate Ship (Columbia, re-rigged) for a colossal Peter Pan vs. Capt. Hook and his crew in a stunt-man's battle-royal.
(At WDW this is a Pocahontas segment. I like Pocahontas, but its just not a great source for ACTION.)
•At the finale, the characters all sail around in the REAL Steamboat (Mark Twain).
(At WDW this is a "cardboard"

ship-like vessel.)
•They rely less on the "water-screens" and more on live action at DL.
(A great many times, the show at WDW will jump too-quickly and too often to the screens.)
•Tom Sawyer/Pirate Island is transformed before your eyes into the amazing Fantasmic! stage.
(WDW's mountain is just fine... but what happens on TSI is astounding!)
DOWNSIDE at DL
And its a biggie... Except for a very few $$ seats, everyone must stand or sit on the pavement to see the show in Frontierland... and there can be a H-U-G-E number of guests crowding into that too-small space to see it.
.