The research decision

[DavidDailey]

Questions about research. 1. Does the investment in research and the cost of upgrades offset the loss of income for building units? In other words is quality better than quantity? 2. Does quantity as Lenin said have a quality all its own? Can a sheer preponderence of units usually overcome smaller better quality units in battles on land and at sea? 3. If you decide to go all in on research is it smart to put money into spying and intelligence first to get faster advances in research categories? 4. Should you correlate your research investment to mirror your opponents?

[calcwerc]

Questions about research. 1. Does the investment in research and the cost of upgrades offset the loss of income for building units? In other words is quality better than quantity? 2. Does quantity as Lenin said have a quality all its own? Can a sheer preponderence of units usually overcome smaller better quality units in battles on land and at sea? 3. If you decide to go all in on research is it smart to put money into spying and intelligence first to get faster advances in research categories? 4. Should you correlate your research investment to mirror your opponents?

Generally: Different countries, entirely different question. The research decisions for all countries differ greatly, so you can not make a general rule on these questions.
1. But when you focuse for each country on what they need, then 1. is a yes. Quality is very important, since it is what makes you able to actually win in a fight. And all losses will effect national morale, which can give you a negative spirale for all countires, apart from Germany where it tends to stay at a very high level throughout the game.
2. I would say no. A Russian army or a British Navy without upgrades will not win the war. 3. This depends. I think it is only a viable option for the US (where intelligence might likely be your number one priority) and maybe Germany (to get an edge in key technologies like tanks). I rarely invest in intelligence for other countries. I sometimes experimented with intelligence for India to counter axis research, but I was not quite sure wether it had an effect.
4. To some degree. But I think your own strategy is more important, since research decisions are mostly done early in the game, and hard to change drastically later.

[ThunderLizard11]

There's not a yes or no answer. If you invest in irrelevant research than no. If you invest wisely than yes. Ask a more spcecific question.

[Zeckke]

i will say; there are two decisions, before 1942 and after 1942

Germany till 1942 quality, after 1942 quantity (armored , antitank, logistics)

United kingdom quality before and after (naval and infantry)

Rusia is the most variable, i use to buy all armored units (first at level 1) as you can then infantry but Rusia should invest in industry to buy infantry.

USA quantity before 1942 and quality after 1942 (air and armored)

Japan quality until 1945 (infantry, logistics, air)

China quantity after and before (infantry and industry)

India quantity after and before (industry and infantry)

besides you have to invest in industry all the game, (all sides).

but more important than research is too buy HQs early

Comand and control and spiying are key research.