Murali is closer to the claim of best in his class when going through spin bowlers than Sachin is to best in his class among batsman; no arguments from me there. But that's apples and oranges for me.
When we're judging who is the 'better cricketer', I view it as a player's ability to enjoy success in the widest variety of conditions and skills against the highest level of players, regardless of whether that's seam bowling, spin bowling, batting v seam, batting v. pace. Sachin had the skills to succeed everywhere and against players of the highest caliber, seam or spin. I don't deny that I view this question in a way that is inherently biased against spinners. Spinners require conditions to be somewhat suitable before they can do major damage. Murali has some gaping holes in his resume, unfortunately for him. I guess I wouldn't fixate too much on getting creamed by Lara, but his performances in India and Australia are the gaping holes I'd always point to. Put it another way, I view Sachin as closer to being a complete batsman than I view Murali as being a complete bowler. I view McGrath and Marshall as more complete bowlers than Murali given their abilities to perform in pace-unfriendly conditions.
[Now is it possible for a bowler to still do some amazing things on a spin-unfriendly pitch? Sure, through dip, drift, and tons of revs, a spinner can always extract something, but we have yet to see it. I'm a huge fan of spin bowling, watching batsmen play spin, and dustbowls, but I have to be honest about a spinner's impact on a cricket match]