All performance data is available in the Wiki.
Sysinfo is a very bad indicator for speed. You should take the time and download the AIBB module, load it in AIBB and then start the "review mode" from the drop-down menu. This will give you good indicators of speed.
Both the ACA1232-50 and the ACA1233-55 have optimized Chipram performance, but they will never be able to compete with a syncronous design like the ACA1230. The old ACA1230 was fully syncronous, which is the fastest-possible way to communicate with the mainboard. However, it's also very piccy in regard to mainboard timing. We've had quite a few support cases where the ACA1230 could not communicate with the mainboard at all, and after I've changed over to an asyncronous design, the majority of these problems were gone.
This brings us back to topic: The ACA500 was also syncronous, but it was not compatible with all A500 boards. The new ACA500plus will be fully asyncronous, and the prototype has already shown that it's compatible with the problematic board revisions such as Rev.3 and the NTSC-Rev.5.