Fortunately, players come in more than two varieties so it's not really an either/or scenario. You want some good scorers (your Datsyuks and Zetterbergs), some secondary scorers (Franzen, Nyquist, Tatar), some complimentary players (basically someone cheap, not necessarily good on their own, but able to play alongside skilled guys and provide decent production - Bert, Cleary, Homer types, in better seasons, Abby), some two-way guys (secondary/tertiary scorer that also provides good defense - Flip, Weiss, possibly Helm, Sheahan), and finish off with some solid checkers (cheap guy, solid defense/PK ability and/or high energy/physicality - Miller, Glenny, Andy). Then try to piece it all together to get a balanced attack with all four lines able to chip in some offense.
Good/secondary scorer - Good scorer - Complimentary guy
Secondary scorer - Good scorer - Complimentary guy
Secondary scorer - Two-way guy - Checker
Secondary/Checker - Two-way guy - Checker
Obviously can be shuffled around based on exact personnel and their positions, and player chemistry, and some players might fit in multiple categories. Basically, I think if a team has Cup aspirations they need to get at least decent production from the third line, and occasional production from the 4th. A team like Pittsburgh is going to struggle more often than not in the playoffs, and most teams that try to build that way aren't going to have players as good as Crosby and Malkin, especially trying to build through trades and UFAs.
With Pav and Hank healthy, I think we have the "good scorers" covered, but of course the more the merrier and one more would sure be nice due to injury concerns. Secondary scoring is our biggest strength, along with checkers. Complimentary guys, mostly Bert and Abby this year, could use improvement. Alfie and/or Legwand could fit in those spots if they came cheap enough. Our two-ways are maybe a little weak, but mostly just from injuries.
To afford it all, the checkers and complimentary guys should be pretty cheap and you need a few others on bargain deals (easiest with young players on 1st or 2nd contracts), with the rest ranging from mid-level to high.
Reality complicates all of that. Getting the right guys isn't easy. Sometimes they're just not available, and even if they are someone else might get them first. Then you have to fit them all under the cap and hope they all gel with each other and your coaching staff and philosophy.