They are better than the other in different ways. 57mm does more DPS, ZiS has more utility.
You're talking about theoretical DPS, not practical DPS. The 57mm has on average 65 less penetration (140/125/115) than the ZiS-3. This is a pretty huge difference as it means the 57mm is going to bounce a lot more shots than the ZiS-3. Since bounced shots don't do damage the great theoretical dps of the 57mm suddenly starts to evaporate against anything better armored than an Ostwind.
I suppose the case could be made that the 57mm is designed to be a sub-par AT gun that can use HVAP rounds to suddenly get a sizable boost in DPS but that brings me to my second point: the 57mm doesn't actually do significantly more theoretical DPS than any other AT gun. The 2.25 reload speed of the 57mm looks good on paper but it fails to account for other factors that affect setup weapon DPS such as wind up, wind down, aim time, and cooldown duration. In the case of the 57mm the wind up and wind down times are about 1.5 times longer than the same times on the ZiS-3. Factor in the extra variables and the 57mm has a RoF of one round every 4.3 seconds. For comparison the RoF of the ZiS-3 is 5.8 seconds and the Pak40 is 4.7. Once you take into account damage the 57mm does 37 DPS, the ZiS-3 does 27.6 DPS, and the Pak40 does 34 DPS.
Edit: I used the old Pak40 stats by mistake and jumbled the 57mm dps numbers. Fixed em now.