If you are comparing Ciresa and Bolduc, you are comparing very similar raw materials.
Despite exactly what country the wood comes from in Europe, most white European spruce is "picea excelsia" or "abies pectinata", with few exceptions. Here in North America, the white spruce used is "picea glauca" or "picea alba". All four species behave as to make their identification solely on characteristics near impossible.
Remember, each tree harvested is different - each processed plank is different, and each soundboard is different. Add to that the customization of ribs, bridges, and work that a particular rebuilder may, or may not, do and it becomes difficult to make a clear recommandation one way or the other with any consistency.
Know that each supplier offers a tremendous product and, IMHO, white spruce would be a great choice if color of tone is your major concern. Sitka may give more power, but usually at the expense of blurring the more delicate pastel shades of tone. The result is that your technician must work harder to bring these out.
In spite of my ramblings, PB summed it all up well when he said:
To be honest it is mostly on the capability of the bellyman
Although I have yet to meet anyone who can make a soundboard perform well using orange crates.