I did touch a little bit on STK before. Sun Microsystems bought STK a little while back and they also have the equivalent technology, but it is a little more siloed. IBM was the first to release LTO-4 with encryption and now HP offers it as well and eventually we will see more of that.
So, there is probably a better portability when using LTO-4, but the technologies are equivalent.
Check out the entire Tape Encryption FAQ.