If you break down their career numbers into averages per 250 IP, Hunter gave up 10 less hits and 16 less walks per 250 IP but gave up 7 more HR and struck out 52 less per 250. A few of those walks were due to Carlton issuing more IBB, though. Pretty much same W-L and ERA, as noted before. There is some evidence that Hunter had a better defense behind him as Carlton had a few more ROE and a few more unearned runs, on average, than Hunter. Also, Hunter's BABIP was .246 vs. Carlton's .284, which may also be evidence of defensive differences (or park factors?) that could at leasty partially explain (if you buy into that) Carlton's higher hits allowed. I do think Carlton's carrying that level of performance, on average, on for 9 more years and 1800 mor IP is pretty darn impressive. Run support is also interesting:
0-2 runs support, Carlton: 1626 IP, 46-160 W-L, 2.99 ERA, 1.24 WHIP, .65 HR/9, .276 BABIP
0-2 runs support, Hunter: 975 IP, 25-103 W-L, 3.26 ERA, 1.15 WHIP, .83 HR/9, .253 BABIP
3-5 runs support, Carlton: 1922 IP, 130-69 W-L, 3.02 ERA, 1.23 WHIP, .70 HR/9, .285 BABIP
3-5 runs support, Hunter: 1417.1, 98-55 W-L, 3.11 ERA, 1.11 WHIP, .98 HR/9, .243 BABIP
6+ runs support, Carlton: 1617.1 IP, 151-11 W-L, 3.62 ERA, 1.27 WHIP, .77 HR/9, .289 BABIP
6+ runs support, Hunter: 1013 IP, 99-8 W-L, 3.46 ERA, 1.14 WHIP, 1.12 HR/9, .242 BABIP
There's some evidence for pitching to the score but I bet this would be similar across all starting pitchers. It looks a little more pronounced for Carlton than Hunter, though.
I didn't learn anything that makes me want to kick Hunter out of the Hall but I think Carlton likely got less help from his defense and/or park and the fact that he was able to perform so well for so much longer than Hunter pushes Carlton ahead of Hunter for me. I am a Phillie's fan, though (bias alert!). And a stat-nerd.