All in the title. Now tell me, who do you think would win, and why? Me and my friend have been having a fight over this...
The Daleks seem a little slow and awkward without a great vocabulary. "Exterminate, exterminate, exterminate". They almost seem too easy to fool and foil. How many times has the Doctor foiled their ill conceived plans. The Borg were no slouches and assimilated hundreds or thousands of advanced civilizations. I think they could easily assimilate the Daleks, yet species 8472 easily could defeat Borg. The ONLY chance the Daleks MIGHT have is if they developed and detonated the reality bomb, which might not have even worked in the first place, and even if it did how would the Daleks stop it from destroying them in the process (in which case they would also lose). Species 8472 had DNA far superior to any human with hundreds of times the code in a DNA sequence. They were psychic. They could control minds and their DNA could infect. We must remember the Daleks are not robots but inferior biological beings not even capable of walking. In one episode a paintball gun was used to attack the Dalek eye. Wow, big defense system. Species 8472 traveled across dimensions from fluidic space and were easily destroying the Borg who were undoubtedly fairly dominant in our realm. Species 8472 had one main flaw, and that was they could be infected by tiny machines who would tear them apart from the inside. It was these nanoprobes that allowed Janeway to negotiate a truce with the Borg. Would the Daleks know this? No. Their technology seems vastly underwhelming. Their reality bomb would likely have fizzled and died. *472 would win without question.
The biggest reason the Daleks are threats is... well, literally put, space armor. They were bullet proof. Normal weapons didn't harm them. They had no empathy or sympathy, so destruction of entire worlds was normal for them. Ship to Ship I reckon the Daleks, en mass, might pose a threat... but 1v1, 8472 all the way. In ground combat, 8472 would utterly destroy them... I can't see the Dalek shell resisting biometric energies very well.
