Yeah, important! I'm new at this, but recently went through the whole boot selection process. I don't know enough about soft flex vs. stiff flex patterns (pipe vs. carving, needs of a beginner vs. those of an experienced boarder, etc.) to warrant a useful opinion in that respect.
However, I can tell you that as an experienced skier, I had no trouble getting a feel for the snowboard wearing a stiff, upper end Salomon Malamute. I was a little apprehensive about my choice because I see many lower-end boots described as "soft and forgiving for beginners", leading me to believe that soft flex is generally perceived as a good trait for us newbies (????). Someone can hopefully explain that!
In any case, I chose this particular boot primarily due to its excellent fit of my foot, secondarily due to its stiffness, and lastly due to its speed laces.
On that note, I notice that of the two boots you mention, the Ruler has Burton's neato speed lace, and presuming an otherwise equal fit of the two boots, I'd definitely give a proven Speed Zone lacing system the nod. Boots are a bitch enough to get right-tight in the lodge, but out on the snow on a chilly day, a quick & simple gloved lacing method is a godsend.
And be sure to check out other brands, too. Just like our ski boots, board boots all fit differently, even amongst different models of the same brand. I tried on various models of K2, Airwalk and Vans before settling on the Salomons.
I wound up with a good, tight fit, similar in most respects to a ski boot, yet quite a bit more comfortable.