My problem with spirals is practice, I just do not do it. I think about it, and I think about using them, but it is really easier for me to just use a regular blade. So far I have only had one thing that was larger than my ex-21 could handle, and I managed with the regular blade. Have to admit though there were times on that project that I looked like I was playing twister.
And the concept of cutting a vein with a regular blade, then going back and using a spiral to make the veining more pronounced, just seems to me to extra work. I just cut on each side of the red line, and voila, distinct veining.