My teacher has suggested I start taking notes on the violas I try out, because it's next to impossible to have all of them here at one time to compare and contrast. So here goes:
little, old viola: it's little, it's old. It's pretty. It makes a surprisingly big sound for a little guy. The D and A sound nice ("creamy," my teacher called it) but the G and especially the C have a bit of shoebox-stuffed-with-newspaper sound.
Stopka: built this year, never owned. Nice sound; last night when my teacher played it, a few notes here and there had such a perfect clear dark viola sound (like a vibrating column of cordovan-colored light appearing in pitch-black dark) that it was like a pleasant punch in the gut, if you can imagine a pleasant punch in the gut. It was nice to realize that this viola was capable of making such a sound. Whether or not I can make it make that sound is another story; it's not the easiest instrument to play. The slightly shorter string length (compared to my viola) is enough to throw my intonation off if I don't pay attention, and my hand frame has gone away, and this leads to left-hand tension as I try to get my bearings, and I get sore/tired more easily. The C string is just about impossible to get a sound from in higher positions (not a happy thing when Scale of the Week = E major sul C). I'm not sure if it's the strings or the instrument or just me. I have to play really near the bridge, very heavy, but not achingly slow.