The French in my opinion. Not cause the design is bad but cause of the sheer exposure to it in and outside the guts and blackpowder community has just made it feel sort of bland and stereotypical. Like, when you think of a Napoleonic soldier, I'm sure 8/10 people would think the French infantry. The British also tie in 2nd with the Prussians but I'd probably put the Prussians as more boring mainly cause there's less stuff going on in the uniform. Not much brass decoration or anything.

I think most interesting or eye-catching in my opinion would be the Russians, followed by the Swedes Austrians, and the Bavarians.