I've used both Litespeed (for about 2 1/2 years) and now SQL Backup for about 7 months.  Overall, both products do the job intended and do it well.

Litespeed has the ability to replace the built in commands of SQL Server so that if you issue the standard backup commands (like using their Maintenance Plans for backups) - you will still be able to take advantage of the compression/encryption.

Both have standalone decompressors, so you can decompress/decrypt a backup on a machine that doesn't have the software installed in order to restore your DB.

SQL Backup does have a Lite version that will allow you to decompress/decrypt the backups from their Pro version - when last I used Litespeed - they did not have this ability - it may have changed now.  This option is great because you can get a lesser version for your developers so that they can restore the DB locally for their own work - without having to have as much space as the full decompressed backup would require.  Plus it's a LOT faster to restore the compressed object, rather than the decompressed object.

I think that SQL Backup does perform better in both compression and encryption time than Litespeed does.  With a big database (mines rather small at 40GB) the faster the better - I get my backup down to about 7gb compressed/encrypted.

I think given all of the issues with people losing hard drives with sensitive information, it's only going to be a matter of time that we hear of some ISP losing a set of backup tapes with companies data on it.  Having it encrypted gives me a little insurance against this happening.  Not to mention the space savings in both backups and that I can now keep a weeks worth of backups on a local drive in case of a failure.

In my own experience, Red-Gate's support staff is more responsive and I got answers/feedback much more quickly from them (even on their forums) than I did with Quest.

Both are good companies and they stand behind their products, so I don't think you'll lose in going with either one.

Bill