"Better" in this respect is very likely a matter of opinion.
The Droid Turbo 2 will most likely at the end of its supported life be running a more recent version of android than the Droid Turbo simply because it is a newer device by 1 full year.
The Droid Turbo 2 has a larger screen but it has a smaller battery. The 2 devices have different processors.
For some, the Droid Turbo 2 would be the "better" device because its specs may be a bit better than the Droid Turbo.
For others, the Droid Turbo would be the "better" device because its price is a bit better than the Droid Turbo 2.
It all depends on your outlook.