That's because you're taking Filppula's ONE good season in there. That's the whole point, nobody believes that that's the player he really is. He finally breaks through and then regresses.
Here's some more telling stats of the top 5 seasons for each player (from best to worst):
Filppula: 66 pts, 40 pts, 39 pts, 36 pts, 35 pts
Weiss: 61 pts, 60 pts, 57 pts, 49 pts, 48 pts.
And Weiss played on a crap team for most of those years.
There is no way Filppula is better.
If you just want to look on the surface, yeah, Weiss is way better than Filppula. If you actually want to know the facts, think about it for more than 3 seconds. Weiss has a much more significant role on the team. He's been their #1 center, Flip is our #3 center. I'll run the numbers for you.
Last five seasons:
Filppula: 328 games, 197 points: .60 ppg
Weiss: 331 games, 231 points: .7 ppg
So he's had a much bigger role on the team with a ton more ice time over a period of time where Filppula often wasn't even on the powerplay and he scored only slightly more.
I'm not saying Flip is better, but there is no argument that Weiss is any better.