Halo wins by a rather large margin for various reasons i'll explain. First off let me just clear up that the precursors are beings on another plane of existence who choose their bodily forms, and one of those forms is of the flood. The flood itself could utterly annihilate the star wars verse. First off the flood/precursors have things called star roads, massive pieces of intertwinned neural physics which are capable of destroying entire solar systems. [quote]We were overtaken by the vast weave of reawakened star roads, spinning and churning like serpents in a huge nest— the graceful and haunting structures of our deep past now made fell and horrifying. The tangle looped around Uthera, deftly avoiding intersecting the planet. Then, incredibly, the planet itself began to crack and shrink, as if squeezed by a huge fist. The resulting shift in our orbit thrust us farther into the mass. An entire planet was being destroyed— just to draw us closer. “This is the way Precursors moved stars,” Maker whispered. Bear, Greg (2013-03-19). Halo: Silentium (Forerunner) (p. 106). Tom Doherty Associates. Kindle Edition.[/quote] [quote]I have watched nine star systems sliced to dust and glowing rubble by star roads— and they used to trace such pretty curves between our worlds. Bear, Greg (2013-03-19). Halo: Silentium (Forerunner) (p. 202). Tom Doherty Associates. Kindle Edition.[/quote] Now that is rather a lot better than the death star. Onto what some people may say, which is to use AI's or robots to attempt to combat the flood/precursors; which is singlehandly the most dangerous and irresponsible thing to do thanks to precursor hacks known as the logic plague. Thhe logic plague is essentially an ability of keyminds (the stage up from a gravemind) which results in any AI in the nearest star system being turned to their side and causing them to attack the original owners. If that was bad enough, the sheer presence of the above mentioned star roads means that most if, not all,technology fails to even work near them. [quote]More alarming, we cannot open slipspace portals; three of our ships have ‘echoed’ from attempted transits and show powerful causality mutations. Some clearly were caught between our continuum and incomplete , inefficient universes. Status of their crews and ancillas is unknown, but communication has ceased. “This system was once a prime site for Precursor artifacts. They are no longer dormant. Suppression fields of enormous power appear to be magnified by local star roads, which are taking on new and startlingconfigurations. “Our weapons are no longer usable. Bear, Greg (2013-03-19). Halo: Silentium (Forerunner) (p. 189). Tom Doherty Associates. Kindle Edition.[/quote] [quote]Suppression fields emanating from retasked star roads and double-bow formations often finish by completely deactivating uninfected ancillas throughout a sector. The vessels that have not been converted are severely handicapped by loss of their AIs. Bear, Greg (2013-03-19). Halo: Silentium (Forerunner) (p. 215). Tom Doherty Associates. Kindle Edition.[/quote]. That's just a few things the precursors could do. The forerunners themselves where crazy, with the ability of travelling to at least 6 other dimensions, having 100km ships made of hardlight, mere one man mechs are rated in megatons to gigatons- with them being capable of causing devastation visible from orbit by the naked eye. TLDR: precursors destroy solar systems, cause ai's to attack their owners, can shut down all electronics in a star system. Forerunners have massive ships, high powered and can use halo rings at varying ranges.