Alan or David??

I have to wonder is there another ending to this film? I think it’s made pretty clear that David is the truly unbalanced one of Jenny’s suitors. Every fault of Alan’s was step up by David in some way and I have to question what would David be capable of if Jenny ever left him. He had no problem ruining his friends life and in the end tried to kill him. I also believe that after overhearing Jenny tell Alan that she loved him David had not only believed he killed Jenny by pushing her over the balcony but had hoped so.
Of the two Alan was by far the better, impulsive as he was he did his best to be honest and it doesn't hurt that he was the better looking of the two.

They were both unreliable and awful.

Alan was unhinged and a manipulative cheater.

David was possessive, jealous, and a "nice guy" of the type who thinks girls "owe him" sex or a relationship because they're sooooooooo different from all the "jerks" and "bad boys" beautiful women usually go out with (in their opinion). David would actually have bothered me way more. I probably would have fallen for Alan temporarily and run from David as soon as he tried to kiss me (because Jenny needed to watch out for cheater Alan, but it was A-OK for David to try to seduce her away from his friend). Poor Jenny deserved better.

They're coming to get you, Barbara!