I've tried 'em both. Periscope is pretty great–no surprise that a service offered by Twitter for integration with Twitter would do so more seamlessly than one offered by a third party.
Verge has a good side-by-side comparison of what's interesting about each app.
Hearts and comments, nico nico-style, are what push Periscope over the top for me.
LIVE on #Periscope: My dog is sleeping and drooling. https://t.co/OMF7kCZsHu
— Xeni (@xeni) March 26, 2015
|LIVE NOW| My dog drooling on Meerkat. #meerkat http://t.co/bQcYIoM6wx
— Xeni (@xeni) March 26, 2015