What if you need to run a third version of the command, or a version that involves deletions, e.g. "less /really/long/path/to/..."?

  bash-3.2$ less /var/log/authd.log.0.gz 
  "/var/log/authd.log.0.gz" may be a binary file.  See it anyway? 
  bash-3.2$ 

I type: control-P control-A meta-D zcat control-E | SPACE less

  bash-3.2$ zcat /var/log/authd.log.0.gz | less

On the OS X terminal, you have to configure it to treat option as meta before the meta-D above will work. I forget whether common Linux terminals require such configuration. (Edit: zless would work just as well here, and on Linux "less" appears to basically have the functionality of zless.)