I guess the YMMV rule here as I have had good results with Astra SP, I dunno what else Id look for. But hope you find some thing AH-mazing
Any suggestions where to start?
Any suggestion will be simply pointless since blades are the most YMMV thing (i.e. I have used Derby blades in my Fatboy for most part of the 90s with excellent results)
So simply try all the blades you ordered and see which one is the best for YOU.
And of course you don't need to shave for a month with a blade to see if it suits you,one shave is more than enough to realize if it is or isn't for you ,it ain't exactly rocket science
If you absolutely want a...POINTLESS suggestion, for ME the absolute best blade for my Fatboy (that I have been using since 1980) is the SHARK SS.
I find feathers to only give me irritation if I apply too much pressure, in a heavy razor they are great and crazy efficientIt was the turn of the Feather blade today.
It felt safe to use not like it was savage or I was going to cut myself but the shave was not as close as expected, one weeper and a lot of irritation.
It's not for me, so far Nacet and GSB have been the class acts.
Perhaps I have already found my two best blades and the rest are going to disappoint.
The cost of the Feather is also not in its favour.
So far it's
1 Gillette Silver Blue
2 Gillette Nacet
I find the Rubies to be great as well. I find they only last for 3 or 4 shaves though compared to a week from the Nacet.
That's handy to know so far I have only been using the blades once, when I have found around 4 blades I like I will order 25 of each and rotate between them.
I have been DE shaving (Slim) since January of 1966, and in all those shaves and through all those blades, I have almost always found the second shave on a blade to be better than the first. My personal favorite in a D4 Fatboy, though, is Feather. Best of luck on your quest; it should be fun, to whichever it leads you.