As far as reading content goes, both apps are nearly identical in this regard. After selecting an article from your library, individual words start flying across the screen at the rate you've selected. Velocity's speed options range from 100 to 1000 WPM in increments of 20 while ReadQuick's scale goes from 50 to 800 in increments of 5 WPM, which I found slightly difficult to control precisely. Tapping on the screen lets you start/stop playback. Both ReadQuick and Velocity display black text on a white background by default but provide an optional white-on-black "night mode." Velocity also provides a sepia tone option.
After having used both these apps for only a short time, I'm not sure if can say my general reading speed has improved dramatically, however, I find that I can now catch up on my reading list very quickly when using either app. In all honesty, though, I had an ulterior motive for my interest in these apps. I like to read while using the elliptical machine at the gym, and reading standard-formatted content on my iPhone can be challenging in that environment. I was on the lookout for a better reading app, and I've found that reading at the gym is now much easier in this format, regardless of reading speed.
At $5, ReadQuick is a tad more expensive than Velocity. However for the additional $2, you get a few extra features in a universal app that's optimized for both the iPhone 5 and iPad screen sizes. (It also works fine on the smaller screen size of older iOS devices.) That said, while I normally avoid running iPhone-specific apps on my iPad, I think Velocity looks just fine at 2x resolution on the iPad's screen.
No matter if you're looking for a tool to help increase your reading speed, help you plow through large amounts of content, or if you're just looking for an alternative way to read on your device, either ReadQuick or Velocity will work just fine. People who read more extensively on both their iPhones and iPads, in addition to Instapaper users who do not pay for a monthly subscription, should opt for ReadQuick. Less demanding readers will likely be satisfied with the simpler, and less expensive, Velocity.
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