I was about to post a question about this but you have more-or-less answered it. That was a while ago so not sure you will even see this, but in case you do:
Just how similar is the hole spacing between the Yamaha and the Aulos? If you look at Lazar’s tenor finger spacing chart (http://www.lazarsearlymusic.com/finger_hole_distances.htm) the plastic Yamaha has almost the worst spacing there is. Lazar’s list isn’t very comprehensive but the 4-5 gap between the Yamaha and, say, the popular Moeck Rotty, is substantially bigger at 47/37mm.
I have the Aulos Robin tenor and the spacing is much easier on that, though I find the lower notes overblow very easily. I also have the Yamaha which is much better in terms of quality, but I would get the Aulos Symphony as well if the spacing was better than on the Yamaha. I don’t find the stretch to the keys on the Yamaha a problem so no point buying the Aulos if that’s the only gain.