The SG Jr is classic and kool and is dripping with mojo. It probably also has horrid fret ends and a low-end, mass-produced vibe typical of lots of cheaper Gibsons nowadays. (Still: it says GIBSON on the headstock.)
I don't think Gibsons
ever feel mass-produced exactly - they seem to still do a lot of the work by hand, and the individual guitars vary a
lot. The trouble is, on the cheaper guitars, that hand-work can be pretty sloppy, and the timber quality isn't always very good either. But if you shop around, you
will find a good one - eventually.
With the SEs, the quality control is better so you're much more likely to be able to pick up a good one "off-the-shelf". To me, that all-the-same quality says "mass-produced", much more than the Gibson - not that there's anything wrong with that. And for $499(!!), it's a steal - the UK price is the equivalent of $800 and I'd say they're still good value.
As the guys have mentioned already, there are also great Jr-style guitars made by other manufacturers, mainly for the Japanese market but available to the World through the wonder of eBay!