I hadn't used Aperture since 1.5. Tonight, I spent 1 hour playing with Aperture 2.1, and I still hate the loupe. That's enough reason for me not to switch. Seriously. It's one of the things I use quite often in Lightroom without even realizing it. Once I didn't have the same level of easy, instant, one (mouse) button access to it, I already felt like I was in foreign lands. When I did use the loupe, I found it to be faster in Lightroom, and just more useful, IMO.
As a Lightroom user, I do like Aperture's layout more than Lightroom's modular setup. I'm not used to Aperture, but I can see the potential benefit of having Aperture's setup. However, I like the "Tone Curve" in the Develop section of Lightroom, and Aperture's equivalent (which I think is using "Levels", I believe) isn't as good. It had more editing features, which I didn't expect. However, I hated doing adjustments in Aperture. The "Spot and Patch" in Aperture is particularly painful. It also felt slow and unresponsive, much like the loupe.
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So things I don't like about Aperture (that I like about Lightroom) are:
1.
The loupe - Big deal for me. Slow, and not as easily accessible as in Lightroom, where I just have to click on the image with my mouse.
2.
No tone curve - Very well implemented in Lightroom. I don't like the "Levels" feature as much in Aperture, and find it unintuitive. I know how to use it, and I can certain get faster by using it more often, but it will never feel right.
3.
Full Screen mode. The Inspector just gets in the way of the photo. I'd rather have it implemented like it is in Lightroom. While you need to hit the "Tab" button on the keyboard to clear everything else, and "Tab" again to bring everything back. To make all the toolbars disappear, just hit the "f" key on the keyboard twice to move things on the screen out of the way.
4.
Adjustments - In the "Develop" module in Lightroom, I like how the adjustment features are sitting on the right side without getting into the way of the actual photo.
What I like about Aperture's layout is how you can access it from anywhere. In Lightroom, you need to go into a the Develop module, so it's a bit compartmentalized. On the other hand, the Adjustments are accessible in Full Screen mode using the Inspector (which I don't like in full screen mode).
I know you can get a similar view in Aperture's "Viewer" mode, where the Adjustment tools are all available on the Left side, but then the toolbar on the top takes up so much space on the screen, making the workspace smaller. I like the dark background of the "Full Screen" view mode, so I'd rather use that, plus have the Adjustments toolbar not block the image while I'm editing.
5.
Spot and Patch.
Wow, that's horrible. It's choppy, and unintuitive. I'm not exactly a computer newbie. I usually understand how to delete. I couldn't delete one of the "spot removal" circles once I put one into the photo. I can access this tool by clicking on the Spot and Patch icon from the bottom of the main "Viewer Only" and "Browser and Viewer" views, and there is no way to delete them if I access it via the icon on the bottom toolbar, I couldn't delete it. It's only after you go into the Inspector and/or Adjustment toolbar that you can delete it. If I'm wrong, then I apologize. I blame it on the unintuitiveness of it. Really. I know it sounds like a cop-out, but I really did spend 5 minutes on this tool and didn't figure out why I couldn't delete until I got to Adjustments.
I also couldn't adjust the size of the "spot" after I set it down. It's annoying. You should be able to resize after putting a spot removal thing down.
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There were a few more things, although I can't remember them right now.
There's nothing specific that I really love about Aperture. I guess I generally like the layout more. Access to metadata is just far better, and is something I don't use in Lightroom as much as I'd like. It takes too long.
Custom naming of files while importing is awesome, and I wish they implemented something similar into Lightroom. I generally like Aperture's "Importing" better.
"Lift and Stamp" is easier in Aperture, although I use the keyboard shortcut in Lightroom so that it's still faster. I found the keyboard shortcut for stamping, but not for lifting. I thought that was weird.
That's it, really. It's not enough reason for me to change over. Lightroom also feels zippier to me.