I think it's important to keep in mind that the Garlean Empire does not rely "more on" either strength or subterfuge. It relies on what is needed to win, whatever that may be. (Note that I mean the overall Empire, rather than one-off madmen like Zenos or Nael.)
Ala Mhigo was conquered through subterfuge, with Gaius stirring dissent and unrest in order to minimize losses on his side. Dalmasca was conquered by brute strength, with Garlean airships bombarding the defenses with impunity until the city fell. Doma might have been a mix of both when it was conquered, and definitely both when the uprising was crushed: the XIIth Legion provided the military might, while collaborators and double agents provided the spycraft. (I don't remember when Yotsuyu betrayed the Domans; I think it was during the uprising? I know the Ninja Job quests deal with betrayal from within regarding the original fall of Doma.)
So it's equally inaccurate to say that Garlemald relies on scheming, or that Garlemald relies on brute force. It all depends on the situation, as well as the individual commanders.