after a shot it takes almost no time before the 103a has the chdk overlay back on the display, with the 102b it takes real time i can count before the chdk overlay is back:)
the cams are identically set up with manual focus active, dark frame disabled, fixed iso, no IS, same make and model sd card (with fairly identical >80MB/s write speeds) and so on. set them up side by side to check.
although it is auto exposure they fire simultaneous and on midday when they both fire at 1/500 or identical shorter there shouldn't be a few seconds difference before they are ready again and the chdk overlay is back on screen wouldn't you agree?
the only visible difference is that chdk flashes once off for some ms during the screen chdk overlay with the 103a while the 102b is just a bit longer dark after a shot until it starts the display for a longer period and then the overlay comes up.
since they both use backlight off after 3 seconds, the 102b always lags a few seconds behind in shutting the display off.
and yes, i always wondered why they didn't do the 103a as firmware update, but perhaps there were changes in hardware that make that leap not possible?