What's wrong with your current bike? at 59,000 km it's still a baby. At 200,000 km you might think about something new. Unless this is just an excuse for a new bike. In that case ignore the above.
As to your question... I've not heard of issues with the cast wheels. They are easier to keep clean. As long as you are not doing gnarly single track they are strong enough. At least that has been my experience.
The spoke wheels look better (IMHO). They are reported to be stronger. If you are planning a lot of truly off road riding (not the dirt roads that some consider off road) I'd go with the spoke wheels. I have heard of some spoke wheel issues. Not a whole bunch, but still.