Earlier quoted context omitted.
> With more consumption and less investment, we expect the economy to increase more slowly than in the counterfactual (no BI). So holding money supply constant (which is of course ridiculous), we'd expect more inflation in the BI scenario than the no BI scenario. Yes, I agree that it seems like there would be more inflation with BI than without it, though, as I said, that will be irrelevant in policy terms as long as…
I think the answer to this question comes from the fact that BI is a policy designed to alter the distribution of wealth, rather than the overall level of wealth. The issue here is not distribution of wealth, it's consumption. The more we consume now, the less we invest in the future. Do you disagree that BI will increase consumption? Concretely, we could invest in reducing CO2 emissions, building Tesla factories or…
The point of BI is to redistribute consumption to the lower end of the economic distribution, at the expense of the higher end, not to increase overall consumption, though that might happen as a side effect.
The net increase in consumption minus the net productivity gains will be the cost of BI, paid to increase economic equality. However, I have seen quite a few (in fact I would say most) proponents of BI argue that the "cost" will be negative, that the productivity gains will, overall, exceed the increase in consumption.
A basis for this claim is that the marginal return on consumption for poorer people is higher than for richer people, and so they can more efficiently use the redistributed consumption, leading to higher overall productivity. The issue of consumption is, therefore, only half of the argument, and must always be considered in tandem with productivity.
The answer to your final question in this context is that we should favour BI because it is intended to increase net productivity at the same time as increasing consumption on the low end: we will have our cake and eat it.