I start out online and switch to the app if/when I hit a snag. Then I stick with the app until that has an issue at which point I go back to the computer. Repeat as needed. Just make sure you're still signed in online. It kicks me off constantly and it can be hard to tell. Hit the "my plans" tab to double check. You can't navigate there if you aren't signed in.
I like using the online site since the formatting seems to work better on a PC and easier to read. Many apps often have display/formatting issues or the buttons to perform various actions get all jumbled. I doubt the success rate/response time has anything to do with which method you use.
I always use my laptop and use chrome for my browser. I can’t work the app as fast and as for browsers, safari always does me dirty when trying to do something “important”
I use phone and tablet, 2 screens one online one MDE ready to reserve dining. I can always guarantee I have issues so swap as needed. Always managed to get there in the end!
Best advice is to use the device you're most comfortable with - most of the time, the device doesn't determine how smoothly the process goes! Sounds like you're having success this morning!!