I hunted phez, chukar, and quail on a very large preserve in NYS for about 20 years. Early on I did the planted bird, and/or tower followup, routine. Afterwards we never put out birds, and hunted the scratch birds in cover the weekenders did not want to go through. And the dogs won't be working "trails" cuz there are none in such places.
Those possessing little or no experience with preserves typically denigrate them. There is a grain of truth - if you put out beach balls and walk them up 20 minutes later you should not expect fast runners and fliers. A phez that's been out more than a few weeks gets pretty savvy. It doesn't take years - or generations - popular myths to the contrary. I think chukar get smart even faster than that.
Preserves offer some flexibility, once you know the preserve and have learned to think with your "bird-brain". If you want a sporting outing with a Model 42, or just wish to host some relative newbies, you can certainly have it. You can also spend the day covering miles to run that one rooster the dogs have been chasing for over an hour. And you can do this stuff from October 1 to April. One blustery day I shot about a dozen phez, with the closest opportunity at 35 yds. I used every bit of a 16 ga M-12 full, and the B&Ps in #5, that day.
When I hosted guys who hunted wild ones out west they mostly said they saw no difference in bird toughness (talking scratch birds), though the judged shot opportunities as a bit closer. Makes sense. That may have been somewhat related to the time of year we were out, too.
Sam