Agriculture
On Milyutin's proposal for agriculture is pretty simple, a survey solely focused on how much grain can be extracted from the peasantry. I'm pretty skeptical of this, as while it may help us extract more grain, it doesn't actually do what the proposal wants, which is gather information so we can modernize agriculture. It would cheaper than the other proposals though.
On a small-p political level, this is him moving against Spiridinova and the Left-SRs. As a Bolshevik member, he disagrees with their takes on agriculture and wishes to centralize it under the party. This seems like a really bad idea. The peasantry doesn't trust us and loves the Left-SRs, while the Left-SRs don't trust us either. By hurting our relations with them, we're hurting our relations with the peasantry, especially given the focus on grain extraction.
Lenin's plan is a very uneasy middle ground. While Stalin, Rykov, and Milyutin are biased against it, I do think they're right in that this is going to lead to a lot of bureaucratic catfights. Milyutin and Spiridinova have differing views on what to do, and so it's not going to be pleasant to work through.
The proposal to support Spiridinova is keeping more to the spirit of what we want with the proposal. It's more expensive, but also more in-depth and likely more effective. On a political level, while it displeases some in the party, it may help keep the Left-SRs on our side. We'll be giving them more of a base, as a result, but worth it to me.
Rykov here is basically arguing for his proposal to support a census. He realizes there's not going to be enough money to do both, and wants the census over the agriculture survey.
Census
On the census I think we're starting to get into the meat of the debate regarding the party-state, why it forms and the benefits and downsides.
Rykov I think is advancing a few things. On a practical level he's concerned over the underdevelopment of the soviet bureaucracy. If we wish to plan an economy we need to have skilled bureaucrats to do so. Otherwise we're going to have vibes-based economic planning. He's not wrong about this, and I do think it would be good to utilize these bourgeois specialists somewhere.
On a political level, I believe Rykov is moving to gather an independent base. The specialists are people that need his patronage to be hired, otherwise they lack effective routes into state jobs. They provide both an effective service and some backing outside the party he can rely on. In addition, he's not playing nice with Skobelev or Kollantai, Food and Social Welfare respectively. While he could just be tired and forgetting to mention them, it does imply that he's aiming to be on top of their departments. After all, aren't food and social welfare just internal affairs?
Looking to Kollantai's proposal on a practical level, she's aiming to use lower-level party members to staff the bureaucracy. By using existing party apparatuses, more people could be mobilized into doing such work. I'm assuming party members don't need to be paid as well as the specialists. Of course, this is optimistic about their capabilities of doing the census. I have no clue how a census back then was run, some of it is just going door to door sure, but I'm skeptical of concluding that's basically all a census is.
On a political level, this is concentrating power in the Bolshevik party, against Rykov's move to establish more power in the state. This does seem more popular in the party itself, as can be expected, with the Chairman, Nationalities, and Education supporting it.
Briefly on Milyutin's mention, I think it's mostly an attempt to make sure his consolidation of agriculture goes through. He's not wrong that doing both hurts, when we'll need the money for economic development, but a census 20 years ago doesn't seem super accurate imo. Lurin's taking a more moderate view of this, and presumably trying to angle against centralizing the bureaucracy in the Bolshevik party.