I have run a lot of Gortex just like everyone else, and I run SnoSeal on all of my non-gortex leather boots
I apply 2x per year. Early spring & late fall. I'm sure 1x per year would be fine, but my boots see a lot of wear and tear. I believe that it keeps the leather in better condition applying 2x. I warm the leather up either in the sun sitting on a reflective surface or in the oven on warm. Then I apply liberally (= messy), and then put back in the sun (or oven with something to catch drippings) to keep the leather warm until it appears that it has stopped absorbing. I then wipe them off.
Is it better than Gortex?: That's a matter of opinion per individual. For me SnoSeal is better than Gortex any day of the week. The reason being is that I have sweaty feet and I will soak a boot from the inside out. In the summer my feet are cooler, and in the winter my feet are warmer with my SnoSeal treated boots
Now for my statement of contradiction:
I still run boots that have Gortex, because I like that particular boot. I have Hanwag Mt Lites, and Keen Steel Toes. Both have Gortex / KeenDry. My Keen's are hot and take forever to dry out. I only wear them in the shop or on a job site. The Hanwag's go on 90% of my hunts. The reasons are both of these boots are comfortable, and get the job done for me. So the pro's outweigh the cons in those situations. If not required then I'm in a pair of cowboy boots treated with SnoSeal
I have no input or experience in using the stuff on Cordura. My off the cuff opinion is that it would not work well on Cordura.