IMO, the Fiesta is supposed to be around the same size of the old Focus. So if you like the size you have and don't feel the need to go larger, I would say go Fiesta. This way you could either save money on the purchase, or get more goodies that you wouldn't get on a similarly priced focus.
The "Superminis" or sub compacts of today are pretty much what the small cars were 10 years ago. I'm not quite sure why it has gone this way. One could argue that Americans are getting bigger fatter and lazier and need larger and more accessible vehicles. However this phenomenon is not unique to American. It looks that Europe and elsewhere has also been going through the size increase.
I would also consider the Kia Rio. I was looking at those the other day and it looks like a lot of car for the money. Especially with the discount they have going on in Canada this month. I don't think I would have considered a Kia of 10 years ago but I don't think their quality of today is anything to worry about.