Lightsail is just renamed t2 instances with storage and bandwidth bundled in. Also, last time I checked (which, granted, was the week Lightsail came out), you can't even check your CPU credit balance on a Lightsail instance. You also can't attach an EIP to a Lightsail instance.
Lightsail is dumbed down to the point of basically being worthless. There's really no reason to use Lightsail over Digital Ocean.