Is it considered backbiting if I say "Muhammad is better than Khalid"?

If the intent behind speaking about Khalid is to expose a fault or deficiency in him, then it is backbiting (ghibah). However, if the intent is to clarify his situation regarding knowledge or trustworthiness, and to advise someone who wishes to deal with him, then it is not backbiting; rather, it is considered sincere advice (naseehah).