ACE (Amethyst Contrast Enhancement, or something like that) is what we're wearing for soft glass these days. ACE has pretty much replaced didymium, but the old terminology sticks around. (As do the glasses. I still have a pair of actual didys.)
Generally, for working colored boro, it's recommended to have a shade 3 (or darker) welding-type lens. Most people find that too dark for working soft glass.
Here's a pair of soft glass lenses with a shade 3 flip-up for a reasonable price. Looks like the flip-up part might be permanently attached, though -- I don't know whether that would get to be annoying. I guess that's an individual thing.
Wale also has what they call
an "SB" lens, which they recommend for soft glass and clear boro (which I suppose puts off less flare than colored boro). It's not recommended for colored boro, but I suppose it would be better than working colored boro with regular ACE (soft glass) glasses.
The price difference may have to do either with the lenses or the frames. Plastic lenses are cheaper than glass lenses. I don't know enough to give an opinion on the advantages/disadvantages of the lens type. Generally, more money will get you better quality frames. If the inexpensive frames fit you and are comfortable, go for it. If you really get the glass addiction, down the road you might or might not want to try different frame styles. (Usually the least expensive frames are too large for me, so I need to go to a price range where there's more choice in styles.)
I wouldn't commit to the split lens style glasses until I'd had a chance to try some on. The ones I've seen are a full glass lens with a half lens, also glass, glued on, which makes the glasses really heavy. Not what I'd want to wear for spending hours at the torch, but YMMV.
You can buy plastic clip-on welder's shades to put on top of your soft glass glasses. I remember hearing something about the color in them fading over a relatively short period of time, so you'd end up replacing them from time to time (six months? A year? I forget.) I heard that some years ago, though, so it might be that technology has improved for even the cheapo clip-ons, so they don't fade.