Urban myth - I have both and have found both to be equally reliable. Windows 7 has changed the game, added to which the hardware in both machines are regular off the shelf parts. An Intel PC is an Intel PC is an Intel PC....period.
I never ever had a crash under XP nor under Windows 7 and I run my machines hard (sometimes 100% CPU utilisation for 12 hours or more) and have some complex software on it.
I am actually finding that restoring a Mac is a pain in the back (side) where with Acronis it is a breeze for Windows (on a machine with BIOS). Similarly having both OS X and Windows 7 natively on the same machine is not very user friendly and virtualisation is just a no-no when running large database applications. ( I'm doing 1.3 - 1.4 billions of records database access per hour in a hierachial database) Restoring is an important issue for me and no easy replication of the TimeMachine backup HDD is another issue. (I might want to go back one or two years with data and do not want old data deleted). If it was not for the form factor and how quiet the Mac Mini is I would leave Apple alone and go back to Windows 7 only. The workarounds required for OS X are not pleasant.... Sure hope that things improve.