I don't think there are any "deal breakers" to decide between the two.
I started with OZRunways relatively early and had trouble with it losing GPS integrity and not telling me. I sent them a number of screen shots of OZrunways showing my aircraft going in a completely different direction than it was.
But now (I think) most of us use external GPS bluetooth units which deals with this issue (and OzRunways may have dealt with this issue). For me the problem occurred repeatably in the low flight levels on route to Mildura near ASWAN.
I changed to AvPlan after these issues, but mainly because (at the time) AvPlan dealt with multi leg flight plans better and I thought was better oriented toward IFR pilots.
I also prefer AvPlans aircraft performance setup and the ability to programme different performance levels depending on altitude and power settings. I like its W&B section too.
I though Ozrunways was a more intuitive programme for point to point VFR flights.
But, the reality is that they are playing a leapfrog race and at any point in time one might have an edge on the other.
I've had cause to call AvPlan a number of times and find them an absolute delight to deal with and Bevan is very accessible to talk about future improvements, change wishlists, etc.
I moved from OzRunways to AvPlan and will stick with them, but I think its a personal preference thing.
The harder decision, frankly is whether or not to keep Jeppesen charts. The last 2 years I have agonised then renewed Jepp as well as Avplan. The Jepp charts are head & shoulders better than Airservices. The question is - how much is it worth above the simplicity of only having one programme.