The answer lies in the grain my friend. And only you can decide that. If you like the look of the grain (and I definitely do) I would spend the time sanding it, because it will pay dividends. If however, you are not keen on the grain or there are slight imperfections in it, then rusticate it. What ever you choose will be the right decision if you stick to the one basic decider 'The Grain'. Don't forget, the first time you use a chisel to start rusticating it, there is no going back.