Do people have a feel (or facts!) for differences in the way MSN and Google index your sites?

I have an established site - going 18 months, good traffic levels, original content, lots of IBL and OBL but only from/to subject-relevant sites, etc. All the main bots come by at regular intervals.

But it rates much better in Google than MSN - for most but not all key phrases. The result is that around 90% of the search traffic comes from Google, with MSN and AOL being the best of the rest but a long way behind.

From the discussions here I take it this is not a typical balance!

Can anyone suggest what MSN looks for that Google doesn't?

Many thanks for any pointers.

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Cheers,
J2Dave