I don't know enough about specifics of realID but here's why something like that COULD be better:
Will be harder to forge than a SS card. Nothing's impossible of course but an NSA-level encrypted magnetic or RFID chip is much harder than a piece of paper that can look like anything. Slap some biometrics on there and even harder.
Will have instant verification - no need to call and check etc
Will replace the circle of supporting documents whereby a VERY easily forged birth certificate or SSN gets you a DL or even a passport if you are clever enough
No need to train all employers, banks, DL bureaus, city, state and county agencies etc on how to verify a huge smorgasbord of different documents such as all possible DLs, birth certifcates and so on. Swipe the card - connect to one database - boom, ID and status confirmed
Will make sharing info between INS, LE agencies etc much easier - one place to look and one place to update.
Personally I would actually LIKE one secure ID that, if done right, could replace a passport, DL, SSN and naturalization or birth certificate, and can only be used by somebody who looks like me (and in the near future or even now with major investment, has my iris scan etc). Identity theft would be much more difficult. Illegal immigration too.
I don't share the extreme loathing of ID or even tracking that some people do here. Without getting into the "nothing to hide" cliché, I fail to see how other people's knowledge of my name and doings, per se, impede on my freedom to do those doings
. To me there's a BIG difference between individuals OR gov't agencies knowing I will be in China 6/18-6/23, own a few handguns, and have a fondness for Guinness and Christopher Moore novels than stopping me going there, owning them or buying them. Sure one COULD lead to the other but that's pretty meaningless. The government knowing my address from my 1040 COULD allow them to kick down my door if the ship-all-immigrants-back crowd gets their way, but I still send one in every year.