Mairi, I think Bobber chose Veronica. She was the one who dramaticized everything just to hook Archie, then turn around and dump him.
Betty, on the other hand, was kind and sincere. Archie never noticed these attributes. I mean, look how Archie is looking at Veronica in that picture you posted. Betty's looking at Archie. And Veronica is sitting there thinking about herself.
Don't it always seem to go that you don't know what you got till it's gone.