I guess it depends on what you actually want to do once you reach your boat???
We found the Thai waters much clearer and better winds than the Langkawi waters (to be fair it could be the time of year that impacts the winds) but not the clarity of the waters l don't think.
It will be much easier to keep it in Malaysia
l would think.
We found RLYC to be not very nice due to its location and the water
movement was very rough during tides changes.
Rebak marina is a great little spot and if you are docked in the marina you are able to use the resorts facilities.
You need to look up Rebak Marina as if you need to get to Langkawi you need to catch a ferry
Telaga seems like a good Marina and is in Langkawi with Customs
, Immigration and Harbour Master all located next to the Marina (very simple).
Again l guess it depends on what you actually want to do once you reach your boat???
We have done the trip from Singapore
to Phuket several times, my comments are based on these experiences.