You've got the smooth version there Rob. Hung's referring to the round, silver "pivot joint" at the top of R2's leg there. They were initially smooth like yours, but a production change was made to the more accurate version with spokes (slotted pegs). As far as I know though, the later slotted peg version only showed up on the R2's that were carded without the insert. Don't think the production change happened in time to get the newer R2's on the older "insert" cards.
I've got a complete set with inserts myself, and found the the first 15 at retail with no problems at all. Dexter was a toughie in this part of the country, and basically nobody was able to find him here so we've all had to trade for him with fellow members. Apparently he was pretty plentiful in other areas though. Odd how that seems to happen so much. I think the reverse was true with the Geonosian Warriors - plenty of them here in Southern California, but a pretty tough find elsewhere.
I had initially picked up both an insert and non insert set of the first 16 figures, but decided that was a bit overboard, and just kept the insert versions after all was said and done. Have the Sacul with insert as well, from our visit to C2 in Indy last year.
To answer your other question, I guess I'd hang on to a less than mint card with an insert, over the same carded figure without one - IF I was putting together an insert set. Not sure what I would do if that wasn't the case, but I'd think most collectors would probably want to at least keep the first 16 figures uniform in their collections - either all with insert or all without. Maybe that's not the case though, but it sounds feasible anyways...