The S and SE have the 2.8 Sonnar, and so are most sought after. But the Tessar (and,less common) Xenar models are fine performers. Can't go wrong with any of them. All work without batteries -- the cameras take the 625 1.3V battery, while the SE and TE take the 6V PX27, which is harder to come by these days. The SE/TE have an LED meter display in the viewfinder, while the others have a match-needle display on the top deck -- which may be a little more stealthy.