Yes it will synch data if you use a publish script. Redgate works for quick and dirty, but if you want to do it write, use SSDT imho.
I'm going to argue with you a bit on this.
We've got a VERY thorough suite of tools for doing soup-to-nuts database development and deployment. You can go from source control through all the environments using our tool set. Further, I'd say overall that we offer quite a bit more functionality than SSDT. Our scripts are safer and we have mechanisms for dealing with data breaking changes that simply causes SSDT to just stop. SSDT is also on a much slower maintenance & upgrade schedule than we are.
Then you start talking about all the other tools available in the suite such as SQL Prompt, SQL Clone, the new data privacy & protection tools, and our offering far exceeds the capabilities and capacities of SSDT.
All that said, SSDT is a very good piece of software, we're just better.
I will admit I have not dealt with Redgate's SQL Clone, I was just commenting on SQL Compare, which is a good tool and does have one advantage over SSDT in that it will create reports of changes. I have used it extensively and before I found SSDT it was indispensible, but if you are a VIsual Studio shop, SSDT integrates so much better using msbuild and the versioning is so much nicer than imbedding it in SSMS.
Still, to each his own, if you like Redgate, by all means use it!