I too have several Coopers and all shoot well. Admittedly, some shoot better than others.
Like others have said previously, I think the smaller calibers make sense for most PD shooting. I shoot 17's (center fire), 19's and the small 20's for 80% of my PD shooting.
However, make no doubt about it, if the wind is blowing seriously and the ranges are getting long, the 20TAC, 204R and 220S come out. (BTW, all are Coopers)
All BS aside, the 204R is a pretty exciting caliber. But, as others have said, you have to watch barrel temps, as you do with all the big powder burners. In high volume shooting, unless you have three of them, you will be passing up shots waiting for the tube to cool down.
Making a decision between 223 and 204 is a tough call. Points can be made for both.
Before I go, let me share two photos that are relevant to my Cooper 204R.
It's a MTV, wood is AAA, barrel is fluted. I have not taken a photo with scope. It is a Lupe VX3 8.5-25X50 with varmint reticle.
Both are five shot groups @ 100 yds.. Load is W748 and 39gr. BK's.
TR, it is not for sale.