PDF compression ? JPEG2000?

I compress my files in Photoshop cs3 and was wondering if it is better to save it for Adobe 1.4 or 1.5.

The reason I ask is that if i save it to 1.5 I can save it as a JPEG2000 which to my surprise decreases the file size by almost a third.

Is there an advantage to this?

Thanks

Ease of file transfer is the main advantage. Acrobat 1.5 is version 7 I believe. So there is a small possibility that your file may not be able to be read on earlier versions, although I have never encountered it.

I am just worried that I will send a portfolio PDF and them not be able to view it and it ruin my chances…

has this occurred before?

That version should be safe. Most places you are sending your portfolio to should have the latest version of Acrobat (Reader at least)