One of my older guns has most of the bluing gone from carry. Should I get it cerakoted, re-blued or just leave it be?

What model of firearm is it? What use will it be put to if finished with a new 'coloring'? What condition is it in now? Is the firearm in the 'collectible' class? Do you live where there is a real rust problem with firearms? Lots of information is needed to be able to give any sort of meaningful advice on your question. .....

That is a personal choice - almost like asking what color car to buy. I PREFER bluing but you need to decide what you like better. To me, guns are "supposed to be" blued. To me, Cerakote is glorified paint. No right or wrong - just your preference.

Note that cerakote comes in many colors, a certified cerakote provider can use a color that looks very much like gun blue or pink or purple or nickel or stainless... the options are mindboggling. They also have a grey finish that is made to add lubricity to internal parts like NP3.

Cerakoting isn't cheap. Before you do it, and I will presume the gun has little to no collector value, you have to decide if it is worth it to you for the gun to look good. I have an old Wells Fargo Model 10, standard 4" barrel, nickel. Carried a lot, for sure, the stocks are well worn and there is plenty of nickel wear. Basically, it is kind of ugly. But it shoots GREAT! There is no way I would waste money having it re-nickeled or coated. Pointless. The decision is yours; pretty versus worn appearance. The gun's function will remain the same.