Hmm, according to the wiki page on balanced swap (same priority), it can be an advantage, no diff or slower, depending on the SD card performance, YMMV. For the wiki page author it was an advantage.

http://wiki.maemo.org/Swap_on_microSD

Have you tried using balanced swap on MMC and SD card on a modern SD card? I am asking just to try to reconcile your two opposing reports.