Compatibility between SX and LE versions?

Hi!

We are currently using Cubase 4 LE, but we want to get back to projects we began years ago on Cubase SX and have been idle since then. I understand that with our Cubase 4 license we can download Cubase 3 for free and then do the conversion to the newer format. But, are there any compatibility issues between SX and LE versions, or are they 100% compatible?

Thank you very much.