Its going to be a difficult choice, my Honda Civic Sport Turbo drives and handles very well but its had a few problems with the alarm system and air con that have been rectified during the manufacturers warranty period, but the niggles spoil the ownership experience.
I’m drawn towards the Mazda 3 because of my experience with owning MX5’s since 1997 and being trouble free motoring. However the Kia Ceed GT is a well kitted out car and performs well.
Don’t get hung up on power figures. I worked for Mazda, in dealerships, when the car was launched last year. On test drives the common thread was that they had read that there was a new, more powerful engine due out and that they wanted to wait for it because “they were worried about the 130 and that they needed more power.” It was an extensive test route, yet not one person saying that the having more power was important at any time accelerated rapidly or in any came even close to high revs, let alone the red line. It happens quite a lot with MX-5 ownership too. The Skyactive X engine is not intended to be a “GTi” but has sufficient power for most situations on the road. It is a nice drive and a nice place to be, unless you are in the back. If I was having a Kia, I think I would get someone to breath on a Picanto and then have some naughty fun that was unexpected.
Try and get a test drive in both. As you will be aware the power delivery will be different as one has a turbo the other doesn’t. But as said above it doesn’t mean they lack power without a turbo. My Mazda2 only has 115bhp and no turbo but is great fun to drive and nowhere near the red line.
It’s how you feel behind the wheel that’s important and also odd as it sounds, imagine both on your drive and which one appeals the most.