Silly question, but I couldn't figure this out by searching the forums: Has anyone assembled a buyer's guide of the pros and cons of the various St. Petersburg blade brands and types made at the PPI factory? I have used Astra SS, Astra SP, Gillette Silver Blue, and Gillette 7 o'clock Super Stainless blades, but the biggest difference that I notice between them is price. Some are smoother, some are sharper, some last longer, etc., but all more or less work well for me, so I go for whatever is for sale at the time.