Since both Opal and ATA Drive Password (via BIOS) methods work by taking advantage of the SSD's inherent ability to hardware encrypt, not only are those methods reliable (assuming no "master password override" exists at the SSD maker or BIOS maker level), but they are impossible to crack once the SSD is powered off. Not so secure if the SSD is in sleep mode, though.
SSDs like EVO, Intel and the like essentially are always 'encrypting' via their controller chips...essentially data comes in, the controller 'randomly' places data someplace on the drive. However, without adding a password, this encryption is open (it's in a safe, but the door is left open) and not secure. Sure, adding an ATA Drive Password in the BIOS will give you no performance hit on the drive and ridiculous security (to the point where you lose the password, you're screwed...unless the BIOS manufacturer has a master password somewhere). The problem with the ATA Drive PW approach: if your machine fries, you need to find another one with a compatible BIOS to enter the password. For fun, do a search for which Mobo's have BIOS's that support ATA Drive passwords. A few do, but no one bothers to mention whether they do or not. Weird. As for Opal, I use Symantec Desktop Encryption for a single Win7 x64 Ultimate (Sophos WinMagic failed, Bitlocker was far too fussy to ever work, the boards are filled with problems initiating it in Win7 ultimate, though it may be easier in Win7) machine- since it works in preboot, there's a 5 second slowdown loading windows, and that's the only performance hit, since it uses the hardware encryption on the SED Samsung 840 EVO.
Bottom line, the hardware security of SED are so solid that you can't confirm the encryption because they are too well encrypted. This is why Mobo makers are nervous about making ATA BIOS passwords available...if the password is lost, all data is gone forever.