To me this is a no brainer. Most of us spend a lot more just on the Golden Shot, gems, or special offers. I played for about six months before picking up an app. I am data oriented so had a little cheat sheet for my club distances and ring adjustments and did okay. But I had to update that sheet when clubs upgraded or I switched clubs and it was a lot of mental calculations during play that often turned to guesses for better or worse… or an occasional time out!!
So, I broke down and bought an app. I put all my clubs in for each bag and after getting used to using the app (I play on my iPad and use the app on my iPhone or vice versa), it made a world of difference. In Tour play, I could look at a hole I knew as it loaded up, choose my bag and ball, put in the wind, put in the elevation and… viola!… I knew the ring adjustment within seconds of my clock starting. It is even quicker in a tournament because I already know the hole, elevation, club, and ball before the hole even loads… so I just put in the wind, look at the adjustment and then can focus on setting up the shot and hitting perfect.
As for the two apps, I have used both and at this point prefer Clash Caddie. For me it is just an easier interface. However, they are pretty much the same as far as calculations (if you turn off the wind direction in Notebook, which I found difficult to work with) and Notebook has a very robust amount of additional value in regard to Tournaments, Courses, and even a Needle Trainer that simulates the shot needle based on club, ball and Tour #.
Regardless of which one you choose, the final benefit is that with an app in hand you can quickly and easily diagnose how to replicate a shot and all of the tournament walk-throughs, tournament text guides, and videos you may find on specific tournament or course holes reference club distance and elevation in the shot set up, along with club, ball and wind of course.
Here are some links to additional thoughts on apps: