Full frame is not sharper than APS-C. It has shallower depth of field when framed the same, requiring a higher f-stop to get more in focus. Why did Ansel belong to the f64 club? Because much less than f64, even with tilts, and not much is in focus. Full Frame has the grim problem of using the bad part of lenses too, making corners truly grim on all but the most fine of lenses.The reason the Canon 1D line of cameras had a 1.3x crop is when it was introduced in 2001, it was the largest sensor Canon could source - as far as I know, it was the largest in a production camera at the time. FF sensors didn't hit the market until the Contax N Digital was introduced in 2002. That same year, Canon introduced the much more successful FF 1Ds. Due to the limits of the technology it had much slower read out, so it was nowhere near as fast as the 1.3x crop sensor 1D. They continued as two lines of bodies - FF for the highest image quality, 1.3x crop for speed. Nikon managed to combine FF and speed with the D3 (although it was slightly slower than 1D mk III and much lower res than 1Ds mk III). The D4 was their successor, and Canon's rather elaborate answer to it was to combine the two 1 series lines with the 1D X.
But, mainly, a pixel is a pixel, and it really doesn't matter what size the sensor was. Full Frame can deliver a better image sometimes, but there is a reason Canon's lead Action camera was a crop body (APS-H). Most likely, tachnology has progressed to the point where the 7D MK II will have better IQ at 1.6 crop than the old 1d MK IV had at its 1.3 crop.
APS-C has some serious advantages. Google "7D bird photography". You will see some amazing things...
Granted, sometime lots in focus is desired. But that's why lenses can be stopped down, and why tilt and shift lenses exist. To get as large a depth of field on FF as on 1.6x, simply use an aperture 1.6x smaller. You will need an ISO just over a stop higher if you want the same shutter speed, but the advantage of FF is still there. And TS-E lenses take things to another level. When you don't want a huge DoF, try a lens like the 70-200 II or the 100L. What's in focus is capable of being so detailed even at the edges of the frame that you'll no doubt be immediately aware of the difference FF makes.
I have shot full frame. I even have a full frame camera. Actually, I have three full frame camera, if you count my Spotmatic and Kiowa. I even have two large format cameras, Crown Graphics.... What I am saying is that full frame is not the all end all. There are times and places and needs for smaller sensors, which will in their case well out perform a larger sensor.
Can you please give us an example of when a smaller sensor would OUTPERFORM a larger sensor? And I just mean the sensor. Thanks.