The value of research

[DavidDailey]

Using a players precious MPPs for research represents an investment that is not made for a more immediate payoff, like a combat unit. But does putting the investment in say production or industrial technology pay for itself with dividends in the future and is this effect amplified with even more investments in these categories in the future? Concurrently, is spending MPPs on say tank research for example more valuable in the long run than building more tanks immediately? If you can hold out in the short run will your investment in the long run prove more valuable, especially if your opponents is going all in to knock you out quickly? In other words, does quality have a quantity all its own and can investments leads (say tank research level 5 to your opponents level 3 as an example) provide an unbeatable advantage? In other words, can you win this game through investment in research?

[Chernobyl]

It's not like that. You have to keep up in research. It's possible to delay research for a few certain other expenses, but in general you need to research early often and fully. It's true that immediate > later, but you're forgetting that techs are global while one unit is just one unit. There's probably dozens of little reasons why techs are better than more units. HQs can only command so many units, geography only permits so many units to fit into an area (think Egypt)....

The only exceptions are France (won't even get your techs before you are dead) and to a far lesser extent China, which sometimes needs to prioritize keeping units in top shape in order to survive the short term.

[Zeckke]

there is no money to research. buy units is the best thing, research depends on IA

[Bavre]

Research vs building units is a very delicate min-max game and getting it right is a large part of any successful strategy. So there's no easy answer here and the only thing that's 100% certain is that both extremes will fail. Having super tech with no units or hordes of level 0 guys is both hopeless, the most efficient solution is somewhere in between and greatly depends on country, enemy research, the amount of immidiate pressure your country is under, what your other countries do etc etc...
Examples:
Enemy goes bomber heavy and you have bad fighters and no AA? More luck next time...
Germany invests heavily into subs and you have no ASW? See above...
You spent all chinese money on fancy research and now Japan is coming full tilt at you so that you're overwhelmed? See above...

Sometimes you can cut corners, for example Italians don't need (and can't really afford) fighter tech. The fighters from germanys minors (Finland, Hungary, Romania) get german fighter tech but can serve under Italian HQs. That way german fighter tech can cover il Duce's ass.

Deciding what to go for is also often just a question of basic common sense, like Japan will never be a Panzer beast while it's very advisable to go for good naval tech with them. Germany is just the opposite.