Argon fill is a good idea.
I'm very surprised at the number of people, including pros, who don't understand what is going on with the argon.
If you put a vacuum between two panes of gas, eventually outside gasses would leak in, primarily through the seals. More importantly, the glass would bow towards the center, making a vacuum sandwich impractical. for that reason, you need something between the panes at approximately the same pressure as the outside environment. That something needs to be dry, no water vapor, or you'll get condensation between the panes. Air would work, but it's easier to get other gasses completely dry. Heavier gasses transfer less heat than lighter ones, so argon is the gas of choice- heavy, dry, relatively cheap.
We now have two panes of gas with argon between them at atmospheric pressure or thereabouts. Pressurizing would bow the glass outward, as well as conduct heat more. In order for the argon to diffuse out, something else would have to diffuse in - else you would gradually pull a vacuum. The lightest, easiest to diffuse gas in normal air is water vapor, it will be the primary component of whatever diffuses in. The first sign of argon leaking out would therefore be condensation on the inside of the pane. The insulation value of the gas fill would not have changed significantly before this occurred. Go with the argon fill.