People hyping Jason's playing over Rob's will never not be funny to me. No, he didn't have some magical ability to fit in with the band's sound better. You could make that argument with Cliff, but not with Jason. He's an unremarkable bassist with a consistently poor tone because he is way too heavy-handed with his picking and it makes the strings sound like shit. Rob runs rings around him, both with regards to raw technical ability and the basslines themselves - he executes Cliff's basslines in his own style, with precision while Jason just sort of plays whatever the guitars are doing with minor alterations. His best performances are on Load and ReLoad, where (by his own admission) his basslines were always worked on and mulled over by Bob Rock, Hetfield and Ulrich. He's not bad, per se, but he isn't in any way special and Rob is better in just about every way when it comes to bass playing, the actual thing he was hired to do. Re: looseness, it's a pretty baseless comparison to make since Rob is dealing with Lars's completely indescribable approach to tempo, while Jason is playing to a pretty consistent one. I guarantee you the string noise his picking makes would be unbearable too if he was playing with Lars of today.