Car shopping is always a fun/frustrating time haha and welcome.
Personally I would look at what is absolutely necessary and required of the car which in my case would be no cvt transmission, fuel efficient, awd, and physical e-brake. Other perks such as radar cruise control sound fun and all but I never use cruise control and probably never will in my life so I cant see the extra tech packages being useful besides just another piece of electronics to go bad eventually.
Since 2016 model cx-3 (first year release) mazda has had some bumps and issues but theyve been somewhat addressed in the later models. 2 of the biggest annoyances of the early models were the ac system condenser(evaporator?) welds being poor causing a leak that drains all cooling capabilities that may happen just as you end warranty. The other big issue I can recall was the infotainment system restarting during cold temps which, after replacing 80% of the entire center console tech and damaging my dash trim, ended up being the sd navigation card reader. Other frustrations are random dash trim vibrations near the A-pillar, low ground clearance that is hard to realize because the lower black trim bamboozles the eye to thinking the car is higher than it really is. Even with these minor annoyances I wouldnt trade it for anything else in their line up. Handling is much more responsive than mazda's cx-5+, 3 and 6 based on the number of loaners Ive driven.
The biggest benefit of the 2019 model you will find is the arm rest setup. Having it integrated as part of the center area is much more stable and better feel than the cheap plastic overhang-over-cupholder piece us lower model commoners have. However this comes with the replacement of the manual e-brake lever to a digital button.
Going back to the beginning question of what I require in a car, the inclusion of the new tech and removal of the e-brake is a deal breaker for me and would probably limit me to getting a 2018 cx-3 if I had to decide but this is just personal preference. That and I also absolutely despise any sort of "tech" that shuts off the engine when I am pulling to a light and then turns it back on when I release the brake.
I would suggest you begin a requirements list of your own in deciding which year is more optimal for your needs and keep in mind that just because 2019 is new and exciting that does not mean it is immune to any issues that may show up down the line. I dont want to seem like a downer for the cx-3 by just listing its cons but its better to know what to expect than to completely regret a purchase because of issues you were not made aware of. Toyota and honda will have their own laundry list of issues as well.
