Which is the better investment?

The 1200 if it is in good shape.
A few caveats.
Don't forget that there are a ton of 1200s. All save a few are used by DJs who abuse the living ----- out of them. What beside form fitted foam a correct box and user manual does "the original packing and everything" mean. I doubt it is secret code language for NOS and unused.
I am curious why you think a table would be broken to bits and stuffed into a bag. Unless, of course, the ad stated for parts or repair etc. only. Even my worst ebay buy came all assembled in one piece with a box and everything, however, some worked for only 4 album sides.
Do you know if it has a a decent cartridge. Even if it did the prior owner would have to have audiophilia.Of course you can salvage the Goldring, which are in the for the money category MM. I own an MMF-5 it came with a better Goldring cart than todays version and I have yet to hear anyone rave about them. Otherwise it will likely be a worn DJ style scratcher and not usable.
The Goldring might be a Rega lite or decontented? Did you get to play it at all? If so you will be able to judge it on it's merits. If it sounds like a Rega you will be in with a slew of Rega fans who find it to be a tremendous table for the money . Always add the money bit.
If you get heavily into the incalcuble numbers of tweaks by starting off with a "better" but not stock arm, you are heading downhill diving face first on that slippery and expensive audiophool slope.
If you play alot of vinyl then, if you can, ante up the bucks and buy a better table. At least a modded by KAB 1200. You do get what you pay for when on the lowest end of the expense curve.

The Goldring table was made for Goldring by Rega. I believe that they have stopped doing so because the Goldring was undercutting the Rega in price. Rega weren't too thrilled about losing sales to a direct competitor that they were supplying. Anyway, the bottom line is that a "real" Rega arm should go well with the table. Given what Mechans has said about the history of a lot of used Technics 1200 arms, I don't think I would risk it. You're only talking a $30 difference on the prices you're quoting. I'd take the Rega arm.

I decided to check out the 1200. It was on Craigslist so I could see it before I bought it. Turned out it was owned by a DJ and I definitely know what kind of damage DJs can do and what to check out on 1200s that have been gigged with. It was one of his three back-up tables and apparently never got used since it was the only silver one he owned. I checked it out and everything I saw confirmed that it was never abused at any point. There wasn't a scratch anywhere to be found and the tonearm and bearings were all in top shape. It was a golden opportunity at the $220 asking price. I definitely plan on buying the RB-250 for the Goldring table when I get some more money saved up.