Feeling? See below:
Adding entries: Pocket > Readability.
I personally like Pocket's way a little bit more. Installing a plug-in is not always working when user need to use a shared computer (like me). Pocket's solution is simpler, and working for almost all browsers.
In my Android phone (Motorola Defy), the story is a little bit different. Both two apps provides "share to ..." for sharing. The difference is the UI response: Pocket is always pops an quick on-screen message fast, while Readability's sharing button has no response until several seconds after. Another problem is Readability sometimes pops up a "adding article fails" message so I have to share it again, while Pocket never fails me.
NOTE: As a man lives in Great Fire Wall, I can't confirm if Readability should be responsible for the last problem.
Sync: Pocket >>> Readability.
I'll say this is the most important reason I like Pocket. In the environment of using my China Unicom ADSL connection, a new post can be seen immediately in Pocket. Meanwhile, I have to wait for a while (probably 2 - 3 minutes) to see it appear in Readability reading list.
Frankly speaking, this issue may not be a deal break: why do I want to see an entry in list when I has already decided to read it later?
I think it's just because of perfection. Who knows?
Page re-formatting: Readability >> Pocket.
Readability wins. With multiple reading theme and clear font settings, the reading experience is more comfortable. Meanwhile, Pocket only allows switching fonts by clicking the same button for several times, which is not intuitive to me.
Add-on for Chinese. One difference between Readability and Pocket for Chinese character is Readability does not use Italic fonts for Chinese characters, while Pocket uses it. Though I personally believe this is a bug, I must say thanks to Readability. This is because Chinese does not use italic at all. As for Pocket, the use of italic fonts makes Chinese articles looks weird.
Night reading mode: Readability >> Pocket.
In one word, I hate the night reading theme from Pocket! There's only one pure black theme for Pocket and it looks ugly. Readability is much better: it offers five themes (wheat, black, light blue, etc.) to allow me choose proper theme for different environments. The most remarkable point is Readability uses a dark grey background for night reading theme, instead of pure black. That makes my eyes much comfortable. My taste, at least.
Subscribing: Readability > Pocket. (You may have different point of view)
Readability offers a subscribing mode, which charges us a small amount to support article writers, $5/month. The 70% of the money will go to the article writers. I didn't see equivalent approaches in Pocket.
Some people may not like it. As for me, I'm fine because I'm always happy to support my favorite writers. So that depends on you. At least, you may choose to decline this without losing any features from Readability.
App memory usage: Both are bad :(.
Well, when saying memory usage, I mean Android. Both apps uses 35+MB memory, which eats a huge block of memory. When I keep both open, my poor phone becomes slow because memory is swapping in and out.
Conclusion? Not yet.
I want to try more, as I'm still new to both services. Moreover, I don't know if I should recommend you guys use them in phone. I personally prefer Evernote if I want to keep an article. If I want to read an article later (and in a cleaner format), I like computer. Anyway, let me try it a little bit more before making a conclusion. I'll keep you updated.