I know some people who have two systems, either by choice or because they have to conform with a work-based productivity system that can't be used for personal purposes.
Originally Posted by tlitterio
My recommendation is that if you have a choice, stick with one system. You're much less likely to lose things, and you want to be able to trust your system implicitly.
Most systems have the ability to use context or a tagging feature to filter for area of focus if you want to see work vs personal. I've found that it's better if I can see both work and personal data together - I often want to do one or two personal tasks during lunch at work and likewise will often do a bit of work from home. On weekends I will filter out my work tasks so that I can forget about them for a while.