Defold is optimized to produce small binaries, and features you don't use can be turned to to further decrease your bundle size.
It also focuses a lot on providing fast iteration times. You can hot-reload changed assets onto a device while the game is running. For most asset types, you'll see the change on device in less than a second. Similarly, a Build and Run cycle from scratch for a moderately complex game project such as Blossom Blast typically takes around a minute or so, and subsequent cached builds can start in a couple of seconds.
(Edit: Full disclosure, I worked on the Defold editor.)
It also focuses a lot on providing fast iteration times. You can hot-reload changed assets onto a device while the game is running. For most asset types, you'll see the change on device in less than a second. Similarly, a Build and Run cycle from scratch for a moderately complex game project such as Blossom Blast typically takes around a minute or so, and subsequent cached builds can start in a couple of seconds.
(Edit: Full disclosure, I worked on the Defold editor.)