Choosing which project advisor to ask recommendations from
Definitely contact them both. The email doesn't need to be the same to each, but inform each that you are also asking the other.
But try to write it in a way that gets you some feedback about what each would write in an actual recommendation: &quot;I hope you view my contributions in a positive light. I found it a valuable experience....&quot;
The senior person's recommendation would have more weight. Both people writing would also be good if there aren't other, better, choices. But you need someone familiar enough with your contribution so that their recommendation seems genuine and not pro-forma.