Is it better to get an LOR from a professor instead of an associate or assitant professor?

[Char123]

Title says it all. The reason I'm asking is because I'm majoring in mechanical engineering and the department only has 3 people ranked as professors. I am only an incoming sophomore and I most likely will only research with associate and assistant professors. Is it a setback to not be able to research with a professor? Would it be less competitive for me to get LORs from associate/assistant professors? Perhaps, by the time I graduate they'll obtain a higher rank.

[Eigen]

No. Not really.

Assistant/Associate/Full grades of professors aren't usually that big of differences- most universities only have a certain number of endowed professorships, and hence a limited number of full professors. Until one of those retires, none of the others can be promoted.

Past that, it's usually a measure of seniority and a measure of pay grade. Generally, associate professors have tenure and assistant professors don't, but in reality you see untenured associated professors and tenured assistant professors.

[runonsentence]

You should get your LoRs from the faculty who know you best and are in the best position to speak positively about your work and your capacity to do graduate-level work in the future.