Two reasons to use MAP:
1) MAP Toolkit is an agent-less tool that does not require software agents to be installed into the target machines (which you want to analyze their Windows 7 hardware compatibility).
2) MAP offers device compatibility of existing desktops for Windows 7 upgrade (i.e. which current device drivers will be compatible with Windows 7 OS).
Have said that, MAP Toolkit is a migration/upgrade planning tool for major Microsoft products. It is not a management tool. SCCM is and it offers great configuration management features that MAP does not offer.
So our recommendation is that if you have SCCM already and you don't mind putting together a comprehensive analysis report of Windows 7 hardware compatibility yourself, you should stick with SCCM. But, if you need to understand existing PCs' device compatibility for Windows 7 upgrades, you may need MAP; and you if you worry about deploying agents to your target machines, you'll really like the agent-less MAP Toolkit.
Lastly, MAP offers other planning features like virtualization candidates assessments of under-utilized servers.
Please do compare these 2 tools carefully since MAP and SCCM are developed for different needs for the most part.
MAP Team
BNg