It's been said many times now by the Devs, They are EXACTLY the same, only the graphic is different.
Now where the problem camos is that with Dragons you can burn thru X amount to find the one you actually want to tame.
With Turtles you gotta get an Egg....then wait 3 days for it to hatch....then hope it's got decent stats (about 1:12 I've found) most have bad stats and you just kill it but it takes so much longer than the 2 hours with GD's.
Give it time and people will be selling R4 Turtles then you will see they are the same.
I have an R4.1 i'm training up and yes, it's the same as the Dragon apart from I can give my turtle temporary extra boost's using the berries found at the champ spawn area mobs.