In a nutshell: If email on the go is your top priority, and you don't like the size and weight of the big BlackBerries, then the 8120 could be a good choice. However, the 8120 lags behind other smartphones when it comes to most features, and it isn't the easiest phone to use either.
The BlackBerry Pearl 8120 is almost identical to the 8100, so read our BlackBerry 8100 review for full details. The 8120 has the advantage of a WLAN connection, and is available in Silver.