A CIC is a horse trial under FEI rules, FEI dressage test, mandatory vet checks (but the timing of those is different now) and *typically* a little bit tougher test for XC level for level (1* = Preliminary and so forth), although the distance of the XC is usually the same at a CIC and regular HT. Nowadays I believe the order is more or less fixed at D-SJ-XC. (correct me if I'm wrong!)
A CCI is the modern-day version of the traditional "three day event" with a longer, tougher XC course.
In the "old days" the distinction was much more clear as the CCI had the full endurance day format with phases A, B, C, and D. (roads and tracks and steeplechase before XC) Nowadays with the demise (other than at the lower levels) of the full "long format" the differences are small and basically it is the order of the phases and the length of XC.
Cross country is usually longer and with more efforts in the CCI events.
From Peter Atkins (helmet cam guy):
CIC is just like a CNC [Horse Trial] but with all the FEI BS like trot-ups and cool down under vet supervision after XC, AND double the cost of entry.
The N in CNC stands for a National event. 1 star is prelim, 2* intermediate, 3* is Advanced. The I in CIC stands for International.
And of course you need CIC's and/or a lower level CCI to qualify for a CCI.
The reasoning for this is if you live in a country where the CNC's (local/national events) are at a very low standard you can't qualify with them and then turn up at Badminton and ride. But it makes it VERY difficult here in America to GET qualified as there aren't that many CIC's or CCI's for that matter. They are such a PINA for the organizers to put on and cost a lot more than normal events.
CCI's used to be long format, ie Roads and Tracks, Steeplechase then XC, which unfortunately no longer exists. Though the XC in CCI's is still approx 50% longer than a CIC. Average 3* CIC is 6 - 6.5 minutes, the average CCI3* is 10.
I think the idea of the USEA setting up a series long format CNC 1*s - Prelim 3DE's (with Roads and Tracks and Steeplechase) is GREAT! I really hope it gets the support and entries it needs to survive from the AA [Adult Amateur] riders.
Clarksdale, MS--the golden buckle on the cotton belt
The FEI is now trying to sell a view that the CICs are just as hard as CCIs. The dressage and showjumping are identical, with the difference being in the length of XC. FEI is now saying that since the CIC intensity is greater than in a CCI of the same level (jumping efforts come up faster and the number is not reduced by the same ratio as the length shortening) .
I swear I see the FEI killing off the CCI over the next few years; and I also believe that "Continental" horses are better suited to the CIC than the CCI. Everything the FEI seems to do degrades the importance of the XC phase. Instead of the traditional grounds for dressage and sj, the FEI now says that these show a horse who is well trained in the "specialist" disciplines as those currently exist.
"I'm a lumberjack, and I'm okay." Thread killer Extraordinaire