excuse me, I just found the Beam width explanation file..
seems like the ez4 is the one with the narrowest beam width so I'll go for that one
The EZ4 also has the shortest range, keep that in mind if range is important. I would suggest the EZ3, as it has about the same width beam but the range is much longer.
I have two problems with the Maxsonar sensors. First, they can't detect objects closer than 6 inches, which in many cases is important. Secondly, while it has a robust set of interface options (analog voltage, serial & pulse width), it's not compatible with most ultrasonic libraries and sketches. This limits you to using their interface code/library or developing your own.
I've never used a Maxsonar sensor so I don't know if there's other issues (like ping speed) which could be important when used as a scanner.
Tim