Obviously I have told all of you a time or two that I find Nicklas Lidstrom to be overrated (more of a #30-35 player than a #15-25 player), so I'll sit here in my wrongness and be wrong, but I'll raise just a few points:
Yes, I think Chris Pronger bridged the gap a little despite the Norris Trophy disparity. At the times of his 2000-01 and 2006-07 injuries, he had his teams in 1st place there was more of a Pronger/Fleury/Sakic or a Pronger/Jagr vibe for the Hart at mid-season. But Chris Pronger is a prolific shot-blocker, and Nicklas Lidstrom is not (usually 3-4 on his own team), and it doesn't take a rocket surgeon to know why blocking shots can be detrimental to the completion of an 82-game season. And I think this (shot blocking) more than some Wolverine-esque healing power kept Lidstrom around ~80 games.
Pronger's 2001 and 2007 teams went from .725/.720 records with him to .468/.469 records without him (essentially an 118-point team vs. a 77-point team with sample sizes of 117 and 48 games). In the playoffs, the Ducks went on to win, while the Blues became the only team from 1996-2002 to break the Colorado/Dallas/Detroit stranglehold on the Western Conference Finals. More than that, he has little or nothing to show from his Norris record in Edmonton and Philadelphia, when his reputation may have never been higher than those Summers.
Granted, it's just 4 seasons, but the three Norris + one 2nd Team selection versus one 2nd Team selection over 2001, 2006, 2007, and 2010 is not at all reflective of Lidstrom and Pronger's value relative to each other. If offered 366 games of Lidstrom or 360 games of Pronger (the actual season and playoff count), give me Pronger.
Those four seasons and three Norris trophies are just a drop in the bucket of Lidstrom though. Nicklas Lidstrom was better offensively and more consistent (though playing on the Detroit Red Wings with that many Selke and Norris teammates would probably go a long way to masquerade any down years).
But if he was as great defensively as advertised, I'd like to think that roster would have challenged for more Jennings than they did (winning in 1996, when Lidstrom was the third-best defenseman on the team; and 2008, when Lidstrom was the third-best player on the planet). 2002, for instance - you have Lidstrom joined by Bowman, Chelios, Fedorov, Yzerman, Draper, Datsyuk, and Hasek; but an habitual run-and-gun team goes into lock-down mode and takes the Jennings by 18 GA?
Certainly the best offensive defenseman of his era, but it's an acknowledgment that means less and less as we see that there was a valley in that era of true offensive talents - inflating his value in a strict positional comparison. Not a big splash internationally, splitting honors on defense with Kenny Jonsson in 2006 (Jonsson winning Best Defenseman; Lidstrom joining Timonen on the All-Star Team). And in some years, you would have a dozen forwards/goaltenders raising their hands when asking who is better than Lidstrom's Norris/All-Star competition. Rob Blake in 1998. Ray Bourque in 2001. 1st Team All-Star Sandis Ozolinsh in 1997. It's not exactly the toughest gold star to receive, and if you take a great forward from the same era, they'd rack 'em up against that competition too - something we put to the test in a Forsberg/Lidstrom discussion a few years back.
If every year was 2000 or 2008, I'm all on-board with Lidstrom=Bourque (minus 1). But I find being in the mix with names like Brodeur, Clarke, Dryden, and Trottier is more appropriate for him.