If you are getting your argon bottles filled at a shop that does a lot of this, what I am about to say won't matter at all. If you have more limited resources (as in my case), it might.
Right now I only have access to a single industrial sized argon bottle for fills. It comes filled at its rated fill pressure, a bit less than 2500 PSI. Having no booster, the best I can do with a 6 cubic foot 3000 PSI bottle is fill it a little over 80% full of argon, and that is only when the argon tank is brand new. Once the tank gets down to 1500 PSI (60% full), I will only be able to fill my argon bottle half full of argon. If I am going to go on a multiple dive trip that will last several days, I will have to top off the bottle with air, and before long I will be using more air than argon.
With such trips in mind, I just got a 13 cubic foot 2000 PSI bottle. When the source tank is relatively full, I will get 13 cubic feet of pure argon, enough to last a bunch of dives. When it's down to 1500 PSI, I will be able to get about 9 cubic feet of argon.
When my resources get better, I will be able to get better fills, but until then...
There was a thread a year or so ago that cited some study in which divers had trouble telling the difference between argon and air when diving, so it might not make that much difference. (I offer no opinion of my own.) I am sure, however, that people will be able to tell the difference between argon and a helium mix.