Using MyBook to back up two systems

I have a MyBook Essential 2.0 320gb.  This is what I’d like to do:  Partition, so that I can back up both my desktop and my laptop.  Use an imaging software to regularly put a new updated image on it. 

I would guess through reading some of these forums that it would be best  to NOT install the software that goes with the MyBook. 

I have Acronis, but noticed Macrium was also recommended.  Either of these would be a good solution? 

What would be the best method of partioning so that I can back up both machines?  This is an area I’m not experienced in, as I have only created one big “partition” whenever I’ve reformatted in the past. 

Any guidance would be appreciated.  If I cannot use MyBook this way - please let me know.