From what I've seen, it is a personal choice.
I have also done both, I prefer air only. Some will blow the lines with air and then pump in antifreeze. They feel the antifreeze eliminates the possibility of remaining water and, it lubes the valves.
Some feel it's quicker to add antifreeze than blow out the lines
Others don't like the taste of antifreeze and find it is necessary to flush the lines several times.
Also, some like air only because they will sometimes go camping during the winter. It's easier to get it ready and then winterize when done.
Everyone agrees, use antifreeze in the traps and toilet.
I've used air only for a few years and have had no problems during our Pennsylvania winters.
Hope this helps.