The answer is .... Kevin!!!!
Seriously. In my opinion, no, McHale was not better overall than KG.
I give the edge in post scoring to McHale (though KG at his peak was pretty [dang] impressive around the hoop as well). But pretty much every other aspect I give to KG.
Even now, way past his 'prime', on offense, KG has actually become almost unreal in how efficiently he puts that long jump shot through the hoop. He shot 48 freaking percent from 16-23 feet last year! You can actually WIN basketball games taking nothing but that shot!
But defense is where KG sets himself apart. I don't think any other player since Bill Russell has had the same kind of overall defensive impact to his team that KG brings. KG's presence on the floor instantly makes any other 4 players world class, top-of-the-league on defense. KG is probably the greatest defender of horizontal space across the paint ever.
As great as McHale was, I don't believe you could put him on the floor with just any 4 players and instantly have a top ranked defensive unit.