You just really can't compare Filppula straight to Weiss. At earliest, you can make some comparison until we have seen a season from Weiss as our 2nd line center, on one of the NHL top teams.
At first, Weiss has been a legitimate 1st line center for years at weak Florida. Yes, he benefits from bigger ice-time on the 1st PP, but he also plays against toughest opposite defensive lines every night. Filppula has never been on that kind of position. He has benefited from easier competition, and that clearly shows in his good ES production. He has been good at it. But he has suffered of the lack of PP time, because of his not-just-good-enough skill level, exact opposite situation to Weiss.
Filppula produced his greatest season as a winger, Weiss has never been a winger. Weiss has had "Bertuzzi", "Franzen", "Hudler", "Cleary" -level wingers at Florida (Fleischmann, Kopecky, Versteeg, Frolik, Higgins, Samsonov), just like Filppula usually at Detroit. But Weiss has never had anybody near at Datsyuk/Zetterberg superstar-level linemates, or teammates to carry the heaviest competition, like Filppula has had all these years at Detroit.
Their recent history is so much different. You really can't compare them 1-on-1 before we'll see same kind of season from Weiss as a contenders 2nd line center or a season from Filppula as non-playoff-team 1st line center.