Beergas vs CO2

I have a nitrogen tank from my old job in heating and air conditioning. I'm getting ready to purchase my first corny keg and start kegging my homebrew. I would like to hear from those who have used co2and beergas nitrogen co2 mix. With that in mind should I use the tank I already have for all types of beer or would you (who has tried both ways) recommend purchasing a co2 cyl for my lighter ales. I know this has been gone over again and again but I have the tank and regulator for nitrogen mix so the cost of equipment would be cheaper to not buy another tank for co2.

Thanks. Clark.

I use both CO2 and beergas, the beergas for my stout tap. I have tried two types of beergas, much prefer the 75%N2/25%CO2 'Guiness' mixture for the stout tap as it does not over carb the beer. 40%N2/60% CO2 resulted in overcarbed beer for me regardless of pressure I set. The bottle connections are different and are not interchangeable. I only use the mixed gas for the stout tap, if I only had one bottle it would be CO2.