I don't think Universal is the right word since they designed the connector and you can't use the old Palm peripherals with it. Enough whining about that. Yes, it accepts both SD memory and MultiMediaCards. That means, trying to prevent piracy for you lawyer-lingo deficient people. Also, they have physical write protection tab to help dummy-proof unwanted accidental erasures.
Size is a huge plus.
The cards are the size of postage stamps. There are drawbacks, though. The memory can be steep. The SD cards are not as readily available and are also much more expensive. Personally, I'd stick to the MultiMediaCard until the SD price drops.