Consensus these days is go with the tweecer. It is the product with the best continuing support which counts for a lot. You also have the ability to switch between multiple tunes with a switch as well as the option of a pricier model with real time tuning capability.
That said I currently own an EEC-Tuner which I bought a few years back and I would not switch to a tweecer with the monetary investment I already made.
If you already have an A3M you could go with either as both support it.
You my also want to have a word with Peter Bysterveld. He is an official supplier of both products and would likely have more practical experience than anyone in Australia with them, especially with respect to support for Australian processors.
His site is here
No personal involvement with his business but we did share plenty of information a few years back before he went pro.