As for my experience I would say - neither side is hard to win.
The only threat for Russians are Togo's fleet which may be completelty evaded at least until second Russian fleet appeared and also Adzumo with Yakumo which in fact are the only significant targets. Unless you self will want tough battles you may not even fight with major IJN forces - just sneak by them - and you'll probably win.
Japanese on the other side may be more agressive in they campaing - the main targets therefore are Russian light cruisers. If you could destroy a couple of them through the first attack at PA - the half of work is done. Then hunt them down splitting AC division to parts untill all of cruisers faster 20knots are destroyed. You may then try to catch Russians on they way from PA lost to Vlad or you may not - it's not significant.
The whole game is about speed not armor or guns. Either to run away from enemy or to catch it up. For example now I have only 7 IJN ships left - and I can't catch them even with just 4 BB cause they run away then I appear
The war is over...