Whenever you mention one film&dev combo here on APUG/flickr/whereever you get about 5 people praising it as the only sensible choice and 10 more condemning it as the worst possible combo. The common saying here (from the really experienced ones) goes along the lines: "If you start, use some standard film&dev combo and only after you mastered them make changes to optimize certain parameters YOU care about - you might not even need to".
Rodinal is said to be a developer with a lot of character but people have made great negatives with it. I am quite surprised that you saw "quite large grain" with ISO 50 film and ANY developer. HC-110 is said to be more of a standard dev so for gaining initial experience it might be a good choice. I'd go with your teacher's recommendations until you have enough experience and skill to photographically stand on your own feet.