My rule of thumb for when a wildcard certificate is appropriate: Is there a DNS wildcard too? For instance, if
foobar.example.com all resolve to the same IP address, it's totally reasonable to use a wildcard certificate. If there are some subdomains that resolve to a different IP address, it's not a good idea to use a wildcard, because someone could turn a compromise of one host (the one with the wildcard certificate) into an attack on other hosts (by MITMing their traffic).
That said, there's another problem with using the maximum number of hostnames on a single certificate: If one of those hostnames breaks, renewal for the whole thing will fail. Figuring out which hostnames failed and reissuing without them can be kind of complicated. I would recommend maxing out your certificates at 25 hostnames.