For safe defrosting, the refrigerator is always the superior option. It maintains a consistent low temperature, preventing bacterial proliferation while the meat slowly thaws. This requires foresight, of course, which can be challenging with a demanding schedule. When I am preparing a Sunday roast, for example, I always ensure the joint is transferred to the fridge a full two days prior. I find it allows me to properly plan my side dishes and accompaniments, something I have been trying to perfect since acquiring my new slow cooker. Last week, I attempted a beef bourguignon, and the preparation simply took over an entire afternoon.