Invite research mentor through SlideRoom or Common App?

I’ve currently invited my research supervisor for a rec through Common App as an Other Recommender, but I’ve noticed that some schools allow you to use SlideRoom instead to submit a research supplement along with the rec.

Will it look bad if I only submit a letter of rec from the research supervisor and don’t submit an additional rec? Since my research was not published, and my supervisor is going to give an overview of my research in the rec, I don’t think my research supplement would add that much new info. But I also don’t want to make it seem like I was slacking.