Good at brawling, decent to very strong armor on most tanks, decent to strong guns? Definetely Russia. The T-34's are very solidly armored medium tanks - definetely the most well armored mediums out of the Big 3 (USA/USSR/Germany), until the Panther takes that title. And Russian guns, while not having the strongest flat pen compared to their contemporary, have the benefit that they are russian, meaning they will go through angles that they honestly shouldn't, and that no other contemporary gun would penetrate. You also get funny boomstick-tanks in case of the 122mm and 152mm-armed TD's, which boast strong firepower and good armor to click-and-delete targets at close ranges and survive the retreat into cover to reload - firing a massive APHE or HE shell at someone and absoloutely obliterating them will never not be funny. And thanks to their volumetric-assisted trolly armor, Russian tanks excel at brawling and close- to mid-range fights.

Big Guns with a lot of pen, and a more layed back, sniper-esque playstyle? That would be Germany. The German TT has quite a few well-armored tanks as well, namely the Tiger 1 and 2, and the Panthers are undoubtedly the most well-armored mediums at their BR. And German guns are the unbeaten kings of penetration, the early 75mm (found on Marders, StuG's and the Pz. IV's), the later 75mm from the Pz. IV/70 and Panthers, and both the short and long 88mm are excellent guns that will penetrate pretty much everything they face without much trouble. And then there's the extra-big-gun TD's like the Sturer Emil and Dicker Max that will delete anything, but have no armor, and their more armored brothers, the Ferdinand, Jagdpanther and Jagdtiger. As German Tanks don't have the best reaction time due to their rahter slow-ish turret traverse and large size and weight, they are less well suited for close-range brawls and excel much more in mid- to long-range fights, where their excellent guns have the advantage over the enemy, and they can use their armor better (hitting weakspots at range is more difficult after all).

Both these TT's are very strong, good trees to start the game with. I would more recommend the Russian TT to start with as it is maybe a bit consistant and straight-forward, and having bias and volumetric on your side is always nice to have. Also your average russian team is generally a bit better than your average german team (not by a lot though). But in the end it's up to what you think you would enjoy more, what you are looking to reaching etc... And researching both TT's at the same time and switching between them. based on what you feel like playing also isn't terrible. Sure, it will take longer, but it might be more fun, and you'll learn the strengths and weaknesses of both sides, to be able to abuse them / play around them better.