I have a miller 210 with the 25/75 mix gas. Mix is all I ever used since I never welded Alum or had a spool gun. Since I have the 250EX now I am wondering if I could use argon for everything in the mig instead of the mix? Any drawbacks other than cost? Reason being I could swap bottles in case I run out with one or the other. Mix gas bottle in the mig is low now so will need to get a refill soon. Ski