I have a Breeze and I am active in a few of the user groups and can tell you that everything “wrong” with the Breeze is fixed with the Spark. To be clear, when I say ‘wrong’, I mean reoccurring pain points with ownership; overall the Breeze is a good drone that I like, but it has its flaws.
1) Battery life is too short. Self-explanatory, however it’s made worse by the shear amount of plastic on the Breeze battery that should have been actual battery cell that could have given it a longer flight time. The batteries are also ‘dumb’, which is not necessarily bad, but I have become spoiled by batteries that manage themselves.
2) No Gimbal. The Breeze takes great photos (within it's scope) but stabilized video never looks as good as a proper gimbal. The pitching the software does to keep the image smooth results in blotchy pixels in certain situations, especially sweeping shots.
3) Range. Varies by device, and I can hit all the geofence limits with an iPhone 7 plus. However, many cannot even get that far. I think this is more Wi-Fi in general and not the Breeze in specifics. I think DJI is smart in hedging their bet with the optional controller. [The Breeze does have a controller, but it is a Bluetooth connection to your device that is still using Wi-Fi to communicate with the drone.]
4) Telemetry. This is one that means more to me than some. All the data one gets used to with DJI Go or Go4 is nowhere in the Breeze Cam software. Mapping, useable flight records, flight time left, etc. I can understand that these may not be needed in a selfie-drone, but competitors (such as the Spark) are including these things and they are useful, even if just to get you interested in what you want in your *next* drone.
5) Smart features. This is the biggest one, and the hardest to explain. DJI Go (and Go4) advise you, the pilot, to the state of your aircraft. It's written from the point of view that you, the human pilot, is in charge and we’re supporting you. The Breeze and its app are written from the point of view that you are an idiot and should not be trusted with flying. Virtually any message that pops up while flying results in an automatic landing. Not good if you’re flying over water! If the flow sensor can’t see because it’s on a dark surface, it won’t take off. Users result to bringing a piece of paper with them to launch from. I was flying over a field where it threw a compass error and auto landed. It was not a catastrophe, but there was zero interaction possible, it just notified me via the app and then landed. It may just be me, but I have concerns about flying something that I'm clearly not in control of.
6) Pack size. This really shouldn't be on here, but let me illustrate something quickly.
Left: DJI Mavic, controller, four batteries, charging hub, power adapter, spare props, car charger, power bank adapter, assorted cables, multiple micro SD cards.
Right: Yuneec Breeze in its travel kit with three batteries. No prop guards, no battery charger, just the drone and three batteries.
I've not seen the Spark kit in person, but the Mavic packs down smaller, with more gear, than the Breeze. I think it would be safe to assume the Spark will pack down even smaller than the Mavic.