Hi there! New user here.
I recently downloaded the Skritter Japanese app to practice for the JLPT. I also recently noticed that there is another app with Skritter Japanese in the name on the App Store:
How come there are two different apps? The Skritter Write Japanese seem to be more recent in terms of mobile design / UX…however, Skritter Japanese seem to be more inline with the current web version with being able to mark cards as Not Yet / So-So / OK / Easy.
Hi @stuartrdr! 
Skritter: Write Japanese is a newer version of the app as you thought-- Skritter Japanese is the original version of the app. On the newer version of the app, you can enable the “Advanced SRS” option in your study settings to set up the 1-4 grading just like the original version of the app. It does by default use a simple 2 grade system. There are also more features available on the new version, for instance kana handwriting wasn’t supported on Skritter Japanese but is supported on Skritter: Write Japanese!