I test drove a Yaris & didn't like it. Sure it's probably a good car but it wasn't for me (that & the fact that the salesman was a total creep - told me it had central locking but I'm not stupid enough to notice him locking both sides of the car after our test drive! Also he drove half of the test drive - what's the point of that?!)
Anyway, the things I didn't like about it were where the speedo was. It just felt so unnatural having it in the centre of the dashboard & the small engine (it struggled to get up a small hill). It's probably great for around town etc but I would have gone mad driving it to work every day (I do 50 miles a day).
It just seemed a bit too small.
But everyone has a different opinion. The best thing is probably to go & drive them yourself & see what you think.