Well, as you've no doubt heard countless times:
Feather Platinums are the sharpest damned things available. You could basically split atoms with them. They are nice, but fairly unforgiving. If your're after the ultimate in baby-smoothness, and your technique is up for it... these are a good pick. I can actually shave closer with a Slant Bar w/ Feather than I ever could with a straight.
Merkur Stainless blades are a nice "mix" for me. Not so incredibly sharp that I'll nick myself, but not so baby smooth, either. Also (compared to Feathers), I feel some pulling/actual cutting of the whisker. Not that it's BAD r uncomfortable, it's just a difference. Many folks actually like this feeling as it lets them know when they're at the proper angle! At first, I was not a fan of Merkurs, but now I see them as a very nice "all around" blade.
Swedish Gillettes are probably my "go-to" blade these days. I still mix-and-match depending on the razor used, etc. But these blades are just a touch sharper than the Merkurs and still smooth and less aggressive than the Feathers. I can (and do) shave with a Merkur Progess opened up all the way with a Swedish Gillette blade and a good soap. I end up with a wonderfully smooth face and no nicks. Granted, if you're careless, you can cut yourself with a piece of loose-leaf paper... But with little pressure and a smooth stroke; you'll be rewarded with a good shave.
I've tried both Astra blades and the U.S. made Gillettes, as well as Personnas. To me, and my face, they all seemed fairly similar and truly dull in comparison to the three blades listed above. Granted, they're pretty forgiving - but for me, the smoothness just wasn't there (without 8 passes or more!). Wilkinson Swords would be smack dab in the middle of this group as well. Not to offend anyone who enjoys these, but I mostly refer the the blades in this paragraph as "second-tier."
I have not tried Derby blades.
Hope this helps.
[FONT=Tahoma][COLOR=Blue]Howard L. Sheppard
"I wish I were less awkward around strangers. I never know what to say when someone asks me who I am and what in the world I'm doing in their house." -- Andy Ihnatko