He was definately a great offensive defenseman and he was definately a great open ice hitter.
Aside from his unknown defensive abilities, I would also be concerned about his below average skating.
I don't really have concerns about Gadsby's defensive game. The only quotes I've ever seen talking about his defensive game make it sound pretty good. I'm sure he wasn't Doug Harvey or Tim Horton out there, but there are a number of quotes saying he was good at both ends of the ice (and none to the contrary, that I've seen).
What we know for sure about Bill Gadsby:
-He was dominant offensively
-He was a major physical presence
-He was an elite shot blocker
I think everyone can agree on those points, and there are plenty of stats and anecdotes to back that up.
Outside of that, most bios mention that he was good at both ends of the rink. I think we can probably take that for what it is. He wasn't a
great defensive player ala Harvey or Horton, but he was a good one. With everything else he brings to the table, I think that's plenty. I can't drop names here, but I imagine his game to be very comparable to a recent elite-level defenseman, but with better offense (pm if you want to know who).
One thing I've gleaned from quotes and bios about him is that his coaches (particularly in New York) liked him playing a very aggressive game. I'm sure that didn't help his defensive game in New York. By contrast, I've heard nothing but praise about his defense in Detroit, where he was used as much more of a stay-at-home guy. For what it's worth, I've seen two different first-hand accounts of his excellent playoff performances with Detroit. Haven't read anything about his playoff work in New York, but his stats at least indicate that he lived up to his billing at the offensive end of the ice.
In terms of his skating, I've seen a lot of conflicting reports. I've seen him referred to as a great skater, and I've seen him called a slow skater. The impression I get is that he lost a lot of speed at the end of his career when he became a stay-at-home guy in Detroit. So at different times he was both, I guess.
BTW, did anyone else know that Bill Gadsby played through polio in his mid-20's?