Just to lay out their point, goal and award finishes...
Daniel Alfredsson
Points: 4, 7, 9
PPG: 3, 4, 9
Goals: 9, 9, 9
GPG: 7, 10
Hart record: 5, 13, 16, 16, 17
Selke record: 4, 10, 11, 15, 20
Brad Marchand
Points: 3, 5, 5, 6
PPG: 4, 5, 5, 6, 9
Goals: 4, 6, 6
GPG: 5, 6, 6, 9
Hart record: 5, 5, 7, 9, 11
Selke record: 9, 9, 10, 12, 12 16.
There's absolutely no denying the two players are close, and I hate to say it, but there's a strong argument for prime Marchand > Alfredsson. He comes out ahead in points, goals, PPG and award voting.
That being said, for overall career value I do think Alfredsson edges out Marchand. Alfredsson has a higher career PPG (0.93 > 0.90) despite playing in 217 more games. This is largely in part due to Alfredsson being more productive in his earlier years. Marchand was a career 50+ point player prior to 28, while Alfredsson already had, 60, 70 points and PPG seasons under his belt before the age of 28.
Alfredsson so far has also aged better, he was an 80+ point player as a 34 and 35 year old. Marchand has 2 67 points seasons the last 2 years. That doesn't even beat Alfredsson's 36 and 37 year old seasons (70+points) it's gonna be hard for Marchand to age as well, he's certainly not on track.