That is, a temporary dip in earnings is unlikely to result in a change in the dividend, or cause management to make the difficult choice to payout earnings that should be allocated to growing the business, both of which would put downward pressure on the price of the stock.
Both Suncor and Cenovus have excellent potential going forward but on the basis of the higher dividend and the lower cost structure, Cenovus would be my choice if you only want to own one.
High dividend tax rates will cause tax conscious boards not to make that choice, opting instead for other uses of free cash flow such as debt-fueled stock buybacks and acquisitions.