I will have them in large window box type planters on my front porch facing East. They get morning sun from 8am about 1:00. Which is the riskier of the two? Also, would alyssum be a good combination plant? (Needing the same amount of light and water)

I really had my heart set on superbells, but wonder if I have enough sun for them....

I'm a newbie and really want these planters to be beautiful this summer :)