HoneyberryUSA has both Romeo and Juliet for Fall shipping this year.
I wonder if the growth difference is due to the soil. In particular, maybe CP handles moist, organic soil better than CJ? Mine is well drained, as it is on a fairly strong slope, but there is a ton of OM, as before I planted anything, I dug out the whole bed. I removed a bunch of rocks and asphalt driveway chunks (thanks previous owners...) and used leaf mulch in this place. After planting, I put down a thick layer of wood chips. CP seems to like this just fine, but CJ has struggled. The row has gotten good light (almost complete sun) for the last year (massive tree to their NW removed), and OK light the year before (after a bunch of trees to their S were removed). The first two years (when one CJ died) they had iffy sun.
I have another spot in the yard where is is relatively dry and very sunny. I planted a CP there and it died a few months later. I replaced it with a CJ and it seems to be doing OK, after more than a year.
Based on the above, I'd be interested to see if someone in the PNW would see a similar growth pattern (better growth from CP than CJ).