I tried a Gillette Silver Blue for the first time this morning. I liked it alot, but it is too soon for me to compare to the Astra Superior Platinum. That said, it seemed sharper that the Astra but time will tell. I've never used a Voshkod.
GSB or Voskhod, I'm happy with either one. GSB is sharper imo but Voskhod is smoother and plenty sharp for my beard, so I prefer it. It's also a bit cheaper than GSB. I get good shaves with Astra, but they're not quite in the same league to me, kind of a gatekeeper. If a blade is better than Astra, then it's among the best. When I think of Astra, I think of "I could've been a contender!" Close, but just not quite good enough.
I don't like the GSBs that I have tried, *at all* - they feel very rough and uneven in my 40s SS. Maybe it's sharp, but not smooth (to me). The Astra is definitely sharper than the Voskhod, and both are smooth. Astra > Voskhod > GSB, for me, in a 40s SS
5 out of 6 to St Petersburg, they must be doing something right