Well, you have to consider how the SERPs interpret the data. Their text based analysis will have human programmed logic (prone to error) combined with several dictionary-driven functions. Google has been the #1 leader in perfecting this technology for a decade.
For a number of years now, work has been proceeding to bring perfection to the crudely conceived idea of a machine that would not only supply inverse reactive search results for use in unilateral phase detractors, but would also be capable of automatically synchronizing cardinal grammeters. Such a machine is the "ranking-encabulator." Basically, the only new principle involved is that instead of pagerank being generated by the relative motion of conductors and fluxes, it is produced by the medial interaction of magneto-reluctance and capacitive directance.
I would therefore consider your choice to between 1keyword.com and keyword-phrase.com to be a marginal issue of the utmost importance. Obviously keyword.com is the strongest preference for branding purposes. However, you must consider what we in this industry amicably refer to as, "SE0 below the belt line."