To me, the problem about the R5 siege on Moscow is that I believe, that Allies, if played well, can drop the odds for that battle below the “healthy” level for Germany. By “healthy” I mean that Germany still loses if they take Moscow with 1 tank and 1 bomber remaining. G5 on Moscow works way better in the Europe game, when Allies can’t bring Fighters from Australia and India to Moscow.
On the other hand, when Axis is played well, I believe Japan has no problem to deal with US buying subs only in California after a J1 DOW. In general, Axis is too strong to be overrun by force early in the game. I am certain the art of defeating Axis is based on wearing the Axis off slowly.
and KJF against J1 is imo worst because it nullifies the price Japan pays for a J1 which is higher US income and US presence in Europe in turn 1. Playing a KJF, Japan has the advantages of a J1 and Germany suffers none of the disadvantages.
But I admit, I am the most boring A&A player in the world. I am not made for dicey attacks and big risks, although I am an absolute advocate of normal dice and I never player low luck so far. :-)