I find it useful to differentiate between reader apps and feed services. Some “apps” are both (e.g., Feedly) but others only act to serve up and sync your content while still others only receive/sync feeds from feed services (e.g., Reeder). Often these apps provide both reader and service but do one or the other poorly compared to competitors. Some of the best apps require an additional feed syncing service for ideal performance, so you’re making two decisions, not one. So, you can mix and match the options… and hence finding the right app/service for me has been frustrating.
I previously used Feedly for the past year or two. On the Mac it’s a web app, but I used Flotato and Nativefier to make it app-like. It provides both a feed sync service and a nice reading interface, with neat and unique tools like backup to Dropbox (I like keeping a real archive).
I’ve recently switched to managing RSS in DEVONthink, though, because I am paying for it anyway and it’ll save me $70 USD/year in Feedly subscription costs. Like your Outlook scenario on Windows, I’m also using DEVONthink already, and keeping more content in the same place seems convenient. That said, DEVONthink requires a bit more manual effort when managing a lot of feed content. (I miss the mark-as-read-while-scrolling aspects of conventional feed apps, for instance.)