You have already driven what many (including myself) consider to be the best small hatchback- the Mazda3. Did you drive the 'i' or 's' model? I'm assuming it was one of the Grand Touring models that you drove. They are the top-of-the-line trim level, the 'i' has the 2.0L engine and 16" wheels while the 's' has the 2.5L engine and 18" wheels (among other minor feature differences). I would highly recommend the 's' Grand Touring 5-door as the one to buy. It's fast, fun, economical, reliable and it has a great audio and nav layout. I've held onto my '06 Mazda3 for 10 years and still love it!
I would advise against the Buick Encore because it is underpowered and overpriced compared to the competition. The fuel economy is also unimpressive and the long-term reliability is questionable, at best.
If you want to consider alternatives to the Mazda3, the Mazda CX-3 and CX-5 (subcompact and compact SUVs) are also very good vehicles. Another excellent small hatchback is the Honda Fit (moonroof standard on EX and EX-L models) but it lacks some of the features available on the Mazdas.
The KIA Soul is another great option. The styling is a love it or hate it proposition, but the feature content and value are hard to beat. You also get a 10yr powertrain warranty.
Still, I think one of the Mazda trio is your best bet...by far!