I've been using Gillette Nacets in my Merkur Futur and getting very nice close shaves. Yesterday I put in a new GSB in it and found it very irritating ATG and I was left with weepers in the moustache area. I'll give it another go to see if its second use is less rough. I know other people swear by GSB but as they say YMMV.
I think it was that particular razor and blade combination.
Today I used my Mercur 37C slant with a new Permasharp blade and had a very comfortable and smooth 3 pass shave with no difficulty or irritation ATG in the moustache area.
I tried the Silver Blue and Platinum (tried the Platinum just today in my Karve), and my thoughts are:
Blade opinion is very much a YMMV and obviously can vary in different razors. But I found both were good blades and wouldn't be disappointed with any of the two, but the Silver Blue felt a tad smoother and sharper, and I found I needed less going over to catch the remaining whiskers/straddlers on my touch up pass with the Silver Blue, when compared to the Platinum. Despite the need to go over more with the Platinum, my face felt great afterwards with no irritation.
The Platinum, felt very similar to me, to the Astra SP Green. But the Platinum beat the Astra on been a bit smoother and a tad sharper.
I used platinum when I was first starting. The razor was an Aristocrat #66. It was decent, but not memorable shave.
GSB on the other hand I tried in bunch of razors and couldn't get a decent shave out of them to save my life. Always rough. Now the Nacet on the other hand is a winner for my face and razors.