I've driven the Mirage, both stick & CVT. The CVT in that car has been in production (used in other vehicles) for 3+ years, so it's not "brand new, untested". And there's a 10 year 100k mi. warranty on it. Despite that, I'd get the stick anyway, personally.

I believe you'll find that pushing 80 mph in either the Mirage or Spark won't be a relaxing drive. Try before you buy.

Also note: despite the drivetrain differences between Spark (82 hp 4-cylinder) & Mirage (74 hp 3-cylinder), they have the same power to weight ratio. Not surprisingly, the Mirage gets better mileage.