Patur Aval Assur,
It’s not loftier in the sense that either way you are really doing it for your own benefit.
This supposed “conundrum” has been answered numerous times in this thread. The difficulty only arises because you are creating an artificial catch-22.
You ask why a person would have any motivation to do something that G-d asks of him/her if it has no personal benefit to him. The only solution you’ll accept to this question is to come up with such a scenario and demonstrate why a person would do it. This is impossible, however, because you have broadened the definition of personal benefit so much that there is no such thing as a scenario where G-d asks something of someone and it has no personal benefit for that person. Therefore, you say, “aha! He’s doing it for the personal benefit! My question stands!”
I think your question is a fallacy designed to be a trap rather than a reflection of reality, and I think that what the sages are saying, that it’s better for our relationship with Hashem to motivate us to perform mitzvos than expectations of rewards, makes perfect sense.