I think Bergeron is arguably the better 5v5 player. With Julien he was playing shutdown minutes with Marchand before his offensive breakout (though Marchand was underrated offensively at the time), and either a young Seguin or a hodgepodge of right wingers, but put up really good numbers.
Over a five year period from 11-12 to 15-16, Bergeron’s was tied with Pavelski for 26th in the league in 5v5 points, and 25th among those with 3000 minutes in P/60. This basically hold for ES numbers as well.
Francis, in the 5 years up to the year he was traded to the Pens was 12th in the league in ES points. His numbers went up in Pittsburgh playing with better players, but I think his Hartford numbers are probably more indicative of how they’d compare offensive at ES/5v5.
Francis was also a very good defensive player, with a Selke win, but I don’t think he’s on the level of someone like Bergeron, who is among the best of all time, and more of the level of a some of the better defensive top line players in the league (like the Forsberg, Sakic, Modano types of his day)Given this and their scoring rates, I believe Bergeron is more likely to outplay a top tier center in a playoff series head to head.
Francis is undoubtedly the better PP player though. Bergeron has become a good PP player in his later years, as he’s improved his shot, but he’s not a guy you want as the main cog on the unit, and at his 5v5 peak under Julien, he received decent PP time and had pretty poor production. Francis meanwhile, always had good PP production whether being the top guy in Hartford or as a complement to Lemieux and Jagr. His vision and passing ability is a level above.
Like at 5v5, I’d say Bergeron is the better PKer as well (and again one of the best ever), though I believe the PK is less important from your top 6 centres.
The question then is whether Francis’ pretty decent PP advantage makes up for the small advantages at 5v5 and on the PK. I think in a overall value sense, it probably does, and would make Francis the better player overall.
If your team lacks an all situations number 1 center and PP QB, then you’re probably going to be better off with Francis. If I’m starting a team though, or I think I’d take Bergeron, because I’d rather have one of the best matchup centres of all time, and hope I could find other players to make a great PP. Especially so if I already have better offensive players, for instance, if I’m building a Team Canada from players of the last 30 years, Bergeron would probably make the team, whereas I wouldn’t really give Francis much consideration.