Everything I have is pre-war, because that's what I found when I was looking. No blasphemy at all. If it works, it works. They key, is how skilled you are/become tuning a plane, and the time/price ratio mentioned by Greg.
Just to show you how crazy different planes/people are, my favorite/best performing smoothing plane is my 1920's era SB #7. Can't get my #3 or 4 to smooth as well as the #7. When I bought it, almost nothing was left of the original blade. Not always a good sign, as you never know if parts have been swapped out. In this case, I think it was the original, as that plane only needed the blade sharpened to perform well.
Just to show you how crazy different planes/people are, my favorite/best performing smoothing plane is my 1920's era SB #7. Can't get my #3 or 4 to smooth as well as the #7. When I bought it, almost nothing was left of the original blade. Not always a good sign, as you never know if parts have been swapped out. In this case, I think it was the original, as that plane only needed the blade sharpened to perform well.