I have the Carver you are looking at, haven't played with the SJC. I think half the issue is the threads they use, I think the SJC uses KKM threads, the Carver uses LW.
Here is a sideways vid of the Carver, shooting some loads that aren't tailored to it. I'll add some more info in a bit.
The loads in the vid are 230s @ 1130ish, loaded w/ Longshot. If they were #9 and a lighter bullet, it would be noticeably flatter. They are pushing back quite a bit, you can see on the last several rounds I get pushed off balance some. My stance wasn't very aggressive, but I was lined up decent behind the gun.
Try not to be blinded by all that flash...
The Jaeger is the same size as the Carver, but uses only holes that face up, FWIW. I think his uses LW threads.
If you are interested in the Carver, I will make you a deal on mine, I don't use it as much since I quit using 10mm brass. Truth be told, I was expecting a larger difference as well, but then, I am not using powders or loads that work the comp very well either. It is a noticeable difference after shooting without it for a while to put it on, the gun shoots a lot faster and with a lot less muzzle rise and torque. For me, the size is the biggest turn-off, I prefer the gun without the extra hanging out the end.
The SJC would probably shoot flatter, since it is longer, has more ports, and is most likely heavier, or at least has more weight hanging out front. To really do it right though, I think you probably need to lighten the slide and your recoil spring, and tailor your loads to the comp and keep them at a fairly low power factor to get anything approaching flat.
I seriously doubt the holes to the side matter much, especially if they aren't in the first port and are smaller, vs. the larger ones on the LW. They aren't doing a whole lot in the first place, so it isn't like they are taking much away from the other ports, and if they weren't there, they would only allow a small amount of extra gas to hit a port farther down the line, which isn't doing that much either.
Some of the gun games forums have a lot of info on comps as well, but it is a lot like asking which powder is best for 10mm, or which barrel, or which gun... :D