I think you and I are perfectly rated to make such judgements. I'll come back later with some great analysis.
What Were Kasparov's Weaknesses as a Player?

Stubbornness. If he would've gave up playing into the Berlin endgame against Kramnik he quite possibly would've never lost a WC match, but he refused to admit that there might be a nut that even GK himself couldn't crack.
and how did he stack up compared to Bobby Fischer's strengths and weaknesses?