I would go for 520 - 2.2l silky smooth six potter, with idrive. 320 is 2.0l four potter. Both are base models, underpowered, but 520 phased out (both engine wise and the entire model) while 320 still in production. 520 may be considered fully depreciated by the time the f10 launched next week. But 320 not yet, once newer model comes out, be prepared for an additional 10-15% depr just caused by new model.