Performs are more complicated, you have to get the groups right or you'll end up in a continuous loop of reconnecting, which your one would do:
1. Perform triggers when you connect
2. /server irc.server1.com (did nothing in testing)
3. /server -m irc.server2.com makes you open a new server window and connect
4. You connect correctly again (see #3), making perform trigger.
5. /server irc.server1.com (did nothing in testing)
6. /server -m irc.server2.com makes you open a new server window and connect
7. Happens again - but this time your nicks are in use so perform doesn't trigger. (End)
While it is possible with performs, its more complicated, and requires that the the first server you connect to is working, or you won't get connected to the second.