According to the AKG site: the TL has a "frequency response above 4 kHz is the same as that of the classic C 12 with a slight high-frequency boost." And "the C 414 B-TL II/ST is a matched pair of C 414 B-TL IIs for stereo recording."
The EBs were discontinued (in the 80s?) and I believe were replaced with the ULS. I've looked at the freq curves on the AKG site, but the gifs are pretty hard to read. It looks like there may be a fairly flat response on axis and a real bumpy one off axis. I say this because it appears as though there are two lines drawn for each pattern except omni.
The XL looks like a newer version of the TL with a "presence boost" and the XLS looks like a newer version of the ULS. Apparently both were made using captured alien technology and have fancy blinking lights that indicate pattern, clipping, off-axis, etc. I think they also have another pattern (maybe sub card). I wouldn't be surprised if they come with cupholders, air conditioning and a force field. Both are available in stereo pairs.