I think J1 brings US to the war too early. I reckon it could be the most effective move in terms of the IPCs you can make your enemies lose in one single turn, and you can easily make up for the 10 IPCs that you will loose for being neutral with the US, but in all the games I played (not a lot yet), US war machine gets rolling and ends up making the Japanese player pay.
J2 lets you position yourself better on the board, as long as you have a clear strategy of what you want to do (go all in for Calcutta, or spread out to get Sydney later on, whatever floats your boat). The problem sometimes is the lack of that clear strategy, I tended to get dispersed and pick a little bit from here, a little bit from there and then get burned.
J3 will make it very difficult for you, because the Allies can stack up forces in Calcutta. In my personal opinion it should be either J1 or J2, max.