I have both Atlas and Harris and I like both and if I had it to do over I would get at least one of each.
Things may have changed since I got mine, but with mine, the Atlas mounts directly to a rail whereas I had to get an adapter to mount my Harris to a rail. This closed the gap in price. IIRC, the Atlas was about $220, the Harris $130. But after the $60 ADM adapter, the gap was closer in price. But then I got 3 inch extenders for the Atlas and opened the gap back up.
My harris is a 13-27 inch and the atlas out of the box is a 6-9 inch, with the extenders the atlas is a 9-12 inch. If I lock the legs forward at a 45 degrees angle I can get it to be a 6-12 inch.
But the Harris can get me up out of the grass on my land, and support sitting (at 20 inch extension) or kneeing (at 27 inch extension) which the atlas cannot do. So for me, I need both.
I also have a tripod to support shooting standing.