I am by no means an expert, so take my comments with a grain of salt.
I recently purchased a VT50, and there seem to be no Panasonic 3D glasses anywhere near me, so I bought 2 pairs of the 4100GB.
I also have 2 pairs of the 3100GB that I got in a 3D starter kit. I only bought the kit for the shrek and megamind movies since the whole thing was $5 clearance at Sears. I did not have a 3D TV when I bought it, and forgot I owned them until I saw this thread.
I tested both sets of glasses and I can say, the 3100GB do work, but text appears wavy and the 3D effect does not POP off the screen. It is almost like watching 2.5D is the best way to explain it. Although the 4100GB are flimsy and uncomfortable, they definitely make the images POP and the text is crystal clear with no issues.
Keep in mind I am no expert, but that is my take after testing them both. If you have any questions or want me to run a different test(please keep in mind my limited knowledge) let me know and I will do my best.