I have a mini ipad 4 with a sim using AvPlan. I'm very happy with the hardware and software. The sim is on a Telstra prepaid plan which costs $50 for twelve months for 5 gig. I only turn on the data if I need to enroute. Most times I can update and plan using wifi. I find it very easy to use AvPlan enroute and to make changes as required. It is also very easy to input plans to Naips. I suspect that we get attached to the system we use first. I have used OZrunways and found it a little cumbersome but that's probably because I am not as familiar with it as I could be. My mini Ipad lives on my leg in the plane and I consider it safely stowed there for landing and takeoff.
For the person who posted earlier and has to swipe the map manually to stay on the page, I think you will find both systems have a moving map mode where the aircraft stays in the middle. AvPlan certainly has.
Both systems and hardware are brilliant and great planning tools. Display brightness greatly affects battery life. I find closing the cover when not needed saves a lot of power. A cheap backup battery or cigarette lighter socket with USB insert keeps it going far longer that I can.
I would say that you should be doing most of your learning about your system when not flying. When flying, keep your head out of the plane as much as possible and use the features of the system you are familiar with.
I did lots of planning at the desk, used the user manual to clear things up and the best tool for learning was comparing notes with fellow pilots. It's amazing that almost every body could contribute some neat feature that others had not yet picked up on.