What distinguishes an HP MSM460 AP from an HP MSM430 AP? 

The MSM460 radios support 802.1n, while the MSM430 radios only support 802.11b/g/ 

All radios on an MSM460 support 802.11n, while only one radio on an MSM430 supports this standard. 

The MSM460 radios support three spatial streams, while the MSM430 radios support two spatial streams. 

The MSM460 supports 802.11n with MIMO on all radios, while the MSM430 supports 802.11n without MIMO.