When choosing professors to write a recommendation for you, it should be as well written as possible (the professor should know and like you as much as possible), and he or she should have a good job title.
Grad students mean nothing. Freshly appointed PhDs are weak. Assistant professors are a bit better, then associate professor, then full professors. Distinguished professors are rare, and i think MD, PhDs are a good bet too.
Which is better though, a full professor who graduated and got their PhD from a moderately respectable university, or
an associate professor who went to Ivy League schools for his/her undergrad & PhD.
Discuss.