The Hellovenizia site has a transport only 3 day Venice Card for 48 euro.
They also have a Tourist 72 hour transport card for 31 Euro (or 33 Euro).
Besides price how do these cards differ.
To begin your analysis, know that a 72 hour pass for the ACTV (public transit system) is 33 Euro and public toilets are 1 Euro. That's pretty much what the transport card offers. The Venice card adds free or reduced admissions for a variety of public museums, so you really have to look at the list to see if you'll want to visit enough of those sites to be worthwhile.