That’s a really broad question. Deciding whether or not to buy a Manchurian IC has a lot to do with your long-term strategy with both Axis powers. It is clearly the most superior factory you can buy (other land options like Kwangtung or French Indochina are not even worth mention). Regardless, I would advise against it.
First of all, a Manchurian IC can really backfire on Japan if you’re not careful, because America can possibly take it over. If America spends a lot of money on a Pacific Fleet, they can successfully cow the Japanese navy to huddle around defend Tokyo, but leave the backdoor open for America to pass a small force into Manchuria just to get control of the factory (or at least ferry units in Northern Siberia). This shouldn’t really happen, but it should be known that you have to be especially careful that nobody will ever take it from you. Undoubtedly though, an extremely wily, smart America can take it from an unviligant Japan.
Anyway, the only thing an IC in Manchuria essentially guarantees is control over central and northern Asia. It also is very useful to crank out fast-moving, powerful threats (tanks) to the dismantle the Russian periphery from the beginning of the game, coupled with serious pressure from Germany on the Western Front. Finally, it allows you to build more than 8 units in the rare occurrence that that is a good idea for Japan. However, it takes a long time for this investment to pay itself off, and a factory doesn’t actually give you any more power over Central and Southern Asia than you would have alternatively have been able to muster with just a transport fleet. You have to make a huge commitment to a large landforce for many rounds of the game, and every turn you do not put three units in Manchuria is not using your factory to its fullest extent. If you ideally buy three tanks per turn, you are deflecting 18 IPC’s per turn to other causes that may need your money more, like a Japanese navy if America decides to build a big fleet. The Manchurian IC doesn’t really contribute to your victory in India (or Asia, for that matter) anymore than a transport fleet does. Ferrying troops from Tokyo to Yunnan and back takes literally the same amount of time as driving down tanks from Manchuria (two turns from the purchase of transports/factory to get a force into Yunnan). Additionally, even though from a mathematical standpoint you would make the most back on your investment by buying tanks every turn there, this can be financially hazardous and the longevity of a Manchurian factory is seriously questionable. Whenever India is taken, a Manchurian factory may not be as useful anymore, especially if Japan starts needing to turn its attention towards America and defending its fragile assets like the money-maker islands.
My final verdict is really to not buy the IC. It can be clutch in certain situations, but a flexible network of transports makes Japan more unpredictable, opens up your options, most effectively utilize’s Japan’s starting forces that otherwise go inactivated, and generally just makes Japan a lot more adaptable to different threats and scenarios. Anyone can feel free to counterargue.
I don’t have time to finish my post but here is the barebones below:
+Permanent fixture in coastal Asi
+Cannot be “sunken” like transports can
+Cheaper in the short-term than building 4 or more transports
+Allows for tanks to threaten Eastern Russia much earlier
+Useful in a KRF Axis strategy
-Cannot make use/activate the large land army spread around useless Pacific islands.
-Not as unpredictable or flexible as a large, mobile transport fleet
-Requires Japan to throw income at Asia for rest of the game
-Mostly serves a single, temporary purpose and becomes obsolete after India is taken
-Not a dynamic threat; cannot be used to defend Japanese territorial possessions in the Pacific, nor threaten the US/ANZAC in a meaningful way
-Transports can take India out directly, avoiding a land route and making it harder for Britain to defend India from the sea
-Can be taken over and used against you
-Does not afford you faster movement of troops around Asia
-Does not make capturing India any faster than a transport fleet