If you can’t do native just yet you have various options. Which is the easiest depends on your situation regarding the amount of IPv4 available and your technical and financial limitations. Keep in mind that for certain solutions like 6to4, teredo and 6rd you still need working IPv4. 6rd and 6in4 can also be made to work with rfc1918 space, but then you are still stuck with the need for nat44 during whatever time the world will take to completely rollover to 6.

My personal preference would be native 6 in a dual stack, optionally followed by either nat64 gateway or DS-lite when you run out of IPv4. If you can’t do native I would try 6rd as this will also survive a v4 run out.

Anything else seems like waste of money and time. Not that these are bad or evil, they served their function. But they have been designed for a situation where v6 would be a fact before the v4 depletion would be there. That unfortunately is no longer the case, we will be out of 4 before the transition to 6 is complete. This requires us to adopt to the new reality.

As a final comment. Any form of tunneling or translation will have it’s impact in efficiency and transparany and should be considered harmful to the original conepts of the internet providing transparant any-to-any connectivity