How large a house are you heating?
Remember 1” pex is more like 7/8” ID, the OD is the same as 1” copper pipe. But since the walls are thicker on pex you lose ID.
I’m heating 2800 sq ft, DHW and 117 feet of sidewalk when it snows, I ran Logstor to the house then one inch copper as not to lose any flow. On smaller houses or heat loads 1” pex will work fine, matter of fact my original lines were one inch but I had a very large temperature drop (Delta T) when everything was pulling heat, now with the one inch copper in the basement and Logstor to the house I stay under a 20F differential.