If you want to jump from 'vi' used when you edit crontab file (crontab -e), just set VISUAL variable to your editor of choice.
For example, to switch from vi to joe, you should do:
# whereis joe joe: /usr/bin/joe /etc/joe /usr/X11R6/bin/joe /usr/bin/X11/joe /usr/X11/bin/joe /usr/man/man1/joe.1.gz /usr/share/man/man1/joe.1.gz /usr/X11/man/man1/joe.1.gz # export VISUAL=/usr/bin/joe
First command is optional of course if you already know where the joe editor is. To make the changes permanent, put in the export line in .bash_profile (assuming you're using bash) in user home folder (our case, root).