Bourque may have been slightly better offensively, but he has so many points because he played against atrocious goalies of the 80's. ( I mean, watch some game from the NHL of the 80's. Looks like different game. Atrocious defensive systems and goaltending)
Hart trophy is incredibly biased, favours forwards almost all the time, not a very good indicator.
As for competition, Bourque may have played against some big name defensemen, but overall there is much more talent now. Bigger, better and faster players. Better coaching system, conditioning, everything.
For me, Bourque is better offensively, Lidstrom defensively. Very close. Lidstrom has had better playoffs, that makes him very slightly better in my book.
Not to mention there was apparent bias towards European players not that long ago.