These deals come and go but for right now probably not too bad if in very good condition w/ 3 mags. Night sights still good? If trijicon you can get them recharged and painted for about 54.00 plus 1 way shipping.
It will run you $600.00 otd for the new gen 4 and you'd probably want night sights + 100.00 to 125.00 or so.
I always like new, but if the trade in, after inspection looks real good I'd probably go with the G-22, but it's a big gun. If you want to conceal it definitely the G23. On second thought I'd probably opt for the G-23 regardless due to size.