You've gotten good answers specific to those things that you can measure or benchmark. But here is one "fuzzy" detail that I've come across:
I've used iView Media Pro 2.x for a long time, and it's done a swell job of managing a quickly-growing collection of RAW and .PSD files.
In moving to Aperture, though, I am finding that I have "found" a large number of images that I had just forgotten about, over time, and have sort of "rediscovered" in Aperture. Obviously, that may be related to my spending more time in front of the program (than I did w/ iView); on the other hand, it may be because Aperture actually does a much better job of getting eyeballs on images more quickly, whether in stacks, side-by-sides, light tables, etc.
This is tough to measure or quantify.
But I've been starting to realize that Aperture is really good at displaying more than just a bunch of thumbnails, and again, I'm finding old(er) .nef files that should have been rated higher (long ago) but weren't. Maybe that has something to do w/ how well Aperture displays thumbnails, and how quickly they can be viewed full size, etc.
Anyway, I guess my point is that Aperture seems to be growing on me, and that I'm finding it easier, faster, and more convenient to view large image collections (and small image collections).
Once you get past the whole "performance" thing, occasional hiccups and speedbums, you find that the application actually does a whole bunch of things unusually well.
Even after just a couple of weeks w/ Aperture, I don't want to go back to iView.
On the other hand, I just spent $500 on aperture software, and another $400 on an beefier video card. Just FYI.
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