The later the better. I still have the first two, 2001 and 2007 and have 2012 in family.
CVT is a very sluggish transmission but the car still has Toyota is every beat. Which means these are extremely reliable cars and being the same Asian yaris spare parts are never an issue for this model. The third generation how ever is different for thai and Malaysian model but still the same for European markets which means spare parts still won't be an issue.
Let's come to driving, as I said previously CVT driving is very sluggish but it can take on a at tranny any time once it comes into action. The car takes time to speedup.
Comparing 2nd and 3rd generation I found 3rd generation 40k driven to be more responsive then my 95k driven 2nd generation
On paper the 3rd gen is longer then the 2nd gen but somehow I found the cabin to be smaller maybe the boot is bigger.
Thirdly 2nd generation has more spaces to keep things the third generation lacks those.
Verdict: I'll definetly upgrade to third generation very soon probably will replace the first gen with it and keep 2nd and 3rd