In zone 5 I'd venture to say neither would be noticeably hardier than the other. After zone 6 winters it's my observation so far that Summer Lace blooms more willingly, but can't say for sure. The color of either flower depends solely on soil pH.

I don't have Summer Lace, but Twist and Shout blooms and grows fine here.

Your blooms will be blue only if you have acid soil or want to go through the efforts to change the soil pH to be acid.