people often view the APS-H sensor as a compromise designed to overcome limitations to full frame based on older slower processing tech, that may have been a large part of its origin
however rather than being a compromise it actually creates a few unique advantages especially when coupled with particular canon lenses
1) The image quality is alot closer to full frame than to crop, its cleaner, sharper basically better all round
the 18MP APS-C sensors have a "fuzziness" about them that the larger sensors dont. they are not bad necessarily however for my personal choice I dont feel they are in the same league as the bigger sensors
And dare I say it they are not as good as the 1.5 Crop sensors from nikon either

2) You still get the lens sweet spot effect, soft corners are gone, lens vignetting gone yep crop has this too and to an even greater degree but the 1.3 crop has a wonderfull balance of IQ and lens benefits
3) a 1.3 teleconverter with no loss of aperture light or image quality
4) the 1.3 crop coupled with the 16-35 f2.8L II make the best walkaround lens on a 1.6 crop the 16-35 is a bit tight for my taste however it gives effectively 21mm to 46mm corner to corner sharp wide open, internally zooming weather sealed with filter not too long not too heavy if the body wasnt to massive on the 1D series it would be the most killer street combo. If you want to see what I mean I suggest hiring a 1D4 and this lens for a day and go shooting. its better than the 24-70 mk1 on full frame however with the MTF on the mk 2 this advantage may be largely a thing of the past. its all down to taste but i really like 20 to 21mm on the wide end and with it hitting up to 46mm its still very usable for portraits
the only 2 advantages APS-C have over APS-H is a bit more reach however APS-H equipped cameras have f8 Autofocus and the APS-C cameras are cheaper / smaller (although i see smaller a disadvantage i find rebels too tiny the 5D size is ideal IMO)
while theres some decent EF-S glass its not better than the corresponding L glass and since it sells for high prices on the used market i dont really see the drama with EF-S compatability when superior L glass on an APS-H camera will out perform the best EF-S on any 1.6 crop just sell and go L

there you go thats all probably worth a good few smites
