i agree with Mik, but having said that there are certain limitations with each package that cannot be overcome.
In terms of what is technically the "best", its either Side Effects' Houdini 5.0 or Softimage XSI 2.0
Both of them are more modular, faster and more stable than any of the competition plus the general features available out of the box kick arse.
Mayas' Mental ray connection pales in comparison to XSIs, which exposes about 99.9% of its features, more with a little SDKing

Hair? XSI already has joe alter Shave And A HairCut and MAX will soon be getting it. Plus SAAHC doesnt look like a bunch of ropey antialiased lines (remember those stills of Dr.Sid from Final Fantasy the movie?)
SubDees? XSI's subdee implementation wipes the floor with everything and even MAXs meshsmooth/NURMS?HSDS is superior to Mayas "true" subdees, which just behave like a particularly crap NURBS implementation.
The only area maya is ahead IMO is particles and its MTOR PRman pipe.
But..when you got mental ray who needs renderman? (well...unless youre doing aload of motion blur and/or dont know C++)
I could go on and on but at the end of the day if you're
that good...you'll find a way round it or just simply roll-your-own.