Bottom line upfront...either of those would be great starter boats to learn on and enjoy weekends and the occasional week or so vacation in protected waters. If that is your intended purpose, the best choice between those models is to pick the one in the best condition.
Now on to the subjectives. If you compare a H31 and a C30 you spouse will likely prefer the H31. If you look at the PHRF numbers(an arguably imprecise indicator of sailing performance)they will probably favor the H31. The boats dimensions are very similar:
H31 C30
LOA 31' 4" 29'11"
Beam 10'11" 10'10"
Dis 9900 10200
The lighter displacement probably explains the better PHRF numbers but other 30's are more in line with the Catalina's displacement so perhaps one could conclude the Hunter is somewhat lighter than it should be for its size. The Catalina will probably have more appropriately sized winches and hardware. The Catalina will likely get the nod for ease of owner maintenence as well, but I never owner either so I can't say for sure. The boats overall come to be a near match just if you look long and hard enough you'll begin to see where decsions were made to hit the price point for the boat.
When I was in your shoes about 5 years ago, I had my sights on an H31, but as my search continued, trying to find that boat in really good shape, I came across a really nice O'day 322, which became my first boat, so I competely agree with Mainesail that condition is the most important factor. For comparisons sake, the numbers on my Oday were LOA 32'2", B 10'8" and Displacement listed as 10250. That boat had a wing keel and was considered a decent sailer for its size/draft.
So long story short, I wouldn't try to talk you out of a H30/H31 that was in good shape, unless there was a C30 close by that was in better condition. Between these two boats for the purpose as outlined above, buying the one in the most pristine condition will set you miles ahead of just selecting one model over the other and limiting your search.
HTH, Good Luck and keep us informed of your progress.