Single gauge co2 regulator vs double gauge?

Hello I am look into to buying a new co2 regulator. An I am looking into buying either a single gauge co2 regulator but what are the disadvantages of the single gauge co2 regulator other then it not telling you how full your co2 tank is?._

Nothing, IMO. In fact the tank level gauge never really works until the tank is empty. Then the gauge shows you that, when it’s too late.

Do you mean single versus dual GUAGE or single versus dual BODY?

A dual body regulator lets you use 2 different pressure settings. So one can be at serving pressure, while the other is force-carbing.

You can use tees or a manifold to keep any number of kegs at one pressure. But different pressures requires a multi-body regulator.

And do look to git one with a knob for adjusting to pressure. I got one you need a screw driver and its a PITA. Not all kegs get the same pressure at my tap room! Sneezles61