I've three yashica's and a rolleiflex (all 127 of course - but some principles apply). The yashica's are really sweet - simple and efficient. re - their lenses, the yashimar lenses are (alledgedy) dodgey, yashikor's OK(ish), and yashinon's good.
My rollei on the other hand is a more advanced beasty - it boasts features like auto-stoping on the winding, and shutter interlock. It even has a feeler to detech the start of the film automatically so you just load the film up and start winding. It's an all toogether more luxury camera. The downside of that is that there's more to go wrong - I suspect the yashica will keep going forever, whereas I had problems with the Rollei, and had to get it repaired. thats the price of the more complex mechanism.
On the other hand the rolleicords are simpler than the rolleiflex, so are probably mechanically more like the yashicas, but check everything is working as it should be.
I'm sure you'll enjoy whichever you choose - as for the sugguestion that TLR's are obsolete, that's just the 70's speaking. My tlr's are smoother, and simpler to operate than any SLR. From a bygone age? That would be the same bygone age as film - sign me up...