Once you get up past 12M, even these days, it is far more about the picture. One with good light can easily be blown up past A3. Also it is about how it is viewed. The point of an A3 or A2 is that it is meant to be viewed from a distance where it 'fits.'
Sure, go up close and you can see the blur or pixilation, but it is not meant to be seen from twelve inches away.
I knew photographers who took pictures of cruise ships for billboards with 35mm and others who would shoot a glass of beer hand shot on 10 x 8" plate camera.
Unless you are going to print pretty well every day I'd avoid ink jet (though their quality can be amazing,) possible problems with drying ink and blocked nozzles. If you are going to print a LOT then get one with big reservoirs.
For irregular use I'd send it out unless you absolutely need to have total control over the printing.