There are several other issues that might play into the decision.

Column-level encryption (CLE) does not allow the indexing of the encrypted column. If that column is in a WHERE clause, that could be a performance issue. Certainly would be an I/O issue, since all rows would have to be loaded and decrypted to check the information for the WHERE. If you use a Certificate (even self-created), then use that to protect a Symmetric key, which in turn is used to protect the data in an encrypted field, then simply restoring a backup to another server wouldn't allow someone to see the data, since the certificate is protected by the Database Master Key (goes with the db backup), which in turn is protected by the System Master Key (does not go with the db backup). Unless this SMK is backed up and restored to the new server before the encrypted database is restored, the data is not viewable by even an SA, since it has no way to decrypt the data correctly. CLE even works in Express Edition! (2005 and up). Much more programming issues, since the encryption and decryption has to be performed (can be mitigated with the use of Stored Procedures to hide the complexity). Varbinary data type is the only data type allowed for encrypted columns.

TDE encrypts whole databases (live data files, backups, tlogs, etc.). It allows normal index usage, since normal datatypes are used for the columns. TDE does require the encryption of TempDB, even if your target database is the only one to get TDE, the TempDB must still be encrypted. That could affect other databases on the same instance, even if not encrypted themselves. TDE is at the I/O level (between the disk and the memory), so the memory is unencrypted, and as such, it does not encrypt data that bypasses the buffer pool (FILESTREAM). No special programming has to be done. All objects are used normally.

A great book on the subject is "Expert SQL Server 2008 Encryption", 2009, Apress, Michael Coles and Rodney Landrum

(I have no affiliation or financial interest in the sale of this book).

Hope this helps.