What "Tag Length" should be used for the EAX MAC?
While the EAX mode permits truncating the tag to any length $\tau$ between 0 and $n$ bits, where $n$ is the block size of the underlying block cipher, this should only be taken as a statement that truncating the tag in EAX mode does not introduce any security issues beyond the obvious (an attacker only needs $2^\tau$ attempts to froge a $\tau$-bit tag by brute force).  Still, in the absence of a particular space or bandwidth constraint that would require a shorter tag, I see no reason not to use a full-length tag ($\tau = n$).

(I suspect the main reason for introducing a variable tag length into EAX was because CCM had one; see the table in figure 4 of the EAX paper you cited.  EAX was designed as a replacement for CCM, and so one of the main design goals was to be able to do anything CCM did, only better.  If EAX had been specified with a fixed tag length, someone might have cited that "missing feature" as a reason to use CCM over EAX.)