I would think that either would be ok, as long as it will handle enough current for the devices that you are working on.
I’m kinda spoiled as I am using this combo 7.5 A variac/wattmeter/dim bulb set that found on the surplus market many years ago:
http://w140.com/tekwiki/wiki/TU-75B
Unfortunately, it does not include a built-in isolation transformer.
jr