It's only more difficult if you
ARE a center controller.
Please let me preface this statement with the fact that I am writing this with only 5.5 hours of sleep under my belt on another 6 day week and man (or women -
in funny Monty Python voice) am I beat and incomprehensible.
I have worked both, as I started out in the ARTCC environment for 6 years at Boston ARTCC. I have found in 22+ years of doing this that the TRACON environment, IMHO, is more difficult. Of course I have only worked busy LVL 12 facilities where the pressure is on to put aircraft 2.5 - 3 nm apart all day long (and into the night) and there is busy satellite airports IE PDK, FTY, etc..
I found that in the ARTCC environment you have a lot of people who are scared (I know I'll get busted for this comment) to work traffic and in the ARTCC environment these individuals where adept a hiding all day. In the TRACON it is such a small environment that there is no place to hide. I used to watch people at ZBW go a whole day without once plugging into position - sometimes for days on end.
Now, of course, with the staffing situation, this is probably not as prevalent as it used to be. Please do not think I am saying that all center controllers are this way because I know for a fact they are not. But with the Snitch machine, 5 nm J-rings, tons of noobies and every other useless tool to make it so they keep planes FARTHER apart rather than closer it's amazing that the aircraft ever get to my doorstep. Nice job ARTCCer's, hope I didn't offend.