Mr. Reader is the best I've found for the iPad, and I've tried several, including Reeder. For iPhone, Reeder might be the best available. I'm still hoping for an iPhone version of Mr. Reader, though.
A couple of reasons I like Mr. Reader:
I can browse my feeds with one hand using the edge-drag based actions, nice if you have an iPad mini
support for left and right handed people
It offers fine grained 'mark as read' controls. I can do older than a day, 2 days, 3 days, a week, 2 weeks, etc. coming from Google Reader this was a must for me.
multiple themes including a good dark a light theme. It has a theming system for users to create themes
mark as read while scrolling, if you want that, which I do
support for many services and a system for connecting ones that the developer hasn't added.
open in different (external) browsers
assign a default view by individual feeds. I can have one feed always show in Pocket view and another in RSS view and easily change it
syncs with a large amount of services. I use Feedbin, but it supports many others
add new feeds right in the app that sync back to the parent RSS service
offline image support
great support from the developer. He seems to be genuinely interested in improving the app and adding support for features
In general it's a well thought out app that came from the days of Google Reader and kept all of its functionality when it went away.
EDIT: the apps site has a good list of other features: http://www.curioustimes.de/mrreader/
I've tried RoN (and everything else)... finally settled on Mr. Reader for a variety of reasons including design, ease of use, formatting, exporting/saving articles to Evernote/Instapaper/etc.