He only real difference is that one is published for you one is not. The published one is a good double check. The MSA is often higher than the LSALT.
Careful there, they're not the same. LSALT will only be the same if there are published surveyed highest points. MSA does not offer you the same 390ft additional buffer that the LSALT calculation does (in the case of none published surveyed points).
However this is all getting very academic practically speaking LSALT is all a NVFR will need. If this is still high enough to necessitate circling down, you will more than likely be doing the same off the MSA.