Looked through the many excellent posts in this thread - a few quick comments:
Also, I like swaping BBs from the East / West Coasts before the end of 1941, so that the 8 BB that go to Pearl really are the worst ones. 3 naval moves by impulse, this is accomplished very quickly.
Usually it is preferred to have the worst BBs/CVs at Pearl in case of Japanese DoW.
However, depending on the overall situation (US chits level, Japanese navy is engaged against CW in NEI/Indian Ocean, or if the US player just likes to play a little risky it may be worthwhile to place the top BB/CVs in Pearl and go for a US DoW, hitting the Japanese hard (the convoy lines or a managable fleet) during the surprise impulse - if the Japanese CVs/BBs are committed already (at sea in NEI or elsewhere) the main US fleet can commit in relatively safety, easily taking out convoy escorts and - if lucky - crippling the Japanese convoy lines (for that turn, at least).
Hitting the Japanese convoy lines are very high priority in order to wear down/take out Japan, I think (of course this is not always possible, but if it is, the earlier the better). (Another top priority is sinking Japanese CVs - once the US get CV/ac superiority Japan is severely hampered.)
Btw, for the AI regarding the Philippines: since return to base is happening after US entry at turn end: if the US is planning to choose the Pearl Harbour or Philippines (or other similar) options at the end of a turn, then it is a good idea to sail out units to sea during the turn, letting them return to base to Pearl or Manila at the end of the turn, after the option is chosen (especially when returning to Manila it may surprise the Japanese, suddently having forces there, making it much harder to capture - just get the TRS out of there quickly, before the declaration of war comes...!
You can never have enough BPs with the U.S. The 8 you spend will be paid back the first 8 turns after you gear-up. After that the rest is all gravy. That is why you should build the factory the earlier, the better.
Without doubt the US will receive more BP overall if building factory (maybe synth as well) early on.
However, this has to be weighted against a number of things, e.g.:
- a unit built earlier will get more 'playing time' (unless destroyed ) than a unit built later
- the US likely wants to go for certain objectives as soon as possible, so the stronger it is when entering the war the better. Spending BPs on factories etc. will mean a few less units early on (but more during the end game)
- time is all-important for the allies, thus it is nice to get going right away
- during the end game the US often has so many units that is becomes somewhat difficult to use the all in an optimal manner (especially taking acitivity limits into consideration) - one for one, I find that a unit is worth more at the earlier stage of the game when there are fewer of them, than at the later stages.
Personally I tend not to build factories/synths, but I think that both options (building or not building factories/synths) are viable. It mainly depends on preferred overall US 'strategy': wanting to have a few more units early on, or more units later on.