Dielectric union or brass union with brass nipple?

[steven712]

Going to install a new Bradford White 50 gallon gas water heater. It has the typical dielectric steel nipples with heat saver. Heard and seen too many issues with those combination steel and brass dielectric unions. So I was thinking about using a solid brass NON-dilectric simple pipeunion threaded onto the tank's steel nipples and then adding a 6-inch brass nipple to which I'll connect stainless flex lines to the copper hot and cold lines. Or do I need to use all brass dielectric unions instead of the simple non-dielectric brass unions? THANKS for your input!!