A Simulated Experiment: Whose numbers are likely more reliable?
This is an interesting way of approaching the problem, but it doesn't convince me, since it seems to make the common mistake of conflating "victory" with territorial gains, when it seems to me that Russia's goals are - at least for now - to degrade and destroy the Ukrainian army ("demilitarization"), and it doesn't take into account some facts, such as that Ukrainian authorities are resorting to more and more extreme measures to draft citizens to the war, nor the fact that since the beginning of the war, not once has Kiev managed to mount a single credible counter-offensive.
The BBC's open-sourced volunteer effort inside Russia to try to find every instance of burials, ceremonies etc... for dead soldiers has (as of late July) confirmed c. 4100 dead Russian soldiers, and sounds credible. Possibly a bit more but I doubt it's much more than 5000. What I think is that Ukrainian losses are vastly underestimated. Note that the Russian estimates for UA killed are from April, this was before even the Ukrainian authorities estimated their losses at hundreds per DAY. It wouldn't surprise me if their losses were actually in the 50-60,000 range. Also, Russian losses are quite "front-loaded" with the biggest proportion coming from the initial months of the war, their number of losses has dwindled since then; it's been a long time that no videos of captured russian soldiers have surfaced in any number, whereas videos of Ukrainian soldiers being captured/surrendering are common, almost daily (and the RU MoD credibly states they have 12,000 prisoners, which should be added to the losses); and we've all seen videos and interviews of both Ukrainian soldiers and foreign volunteers describing units suffering losses in the range of 30-50% KIA/MIA in a matter of days (catastrophic losses) without EVER even seeing a Russian soldier, just from continuous artillery strikes.
I think the Ukrainian army's situation is much more dire than most people are aware of.
Problems are that Ukranian losses are easily hidden by the fact that in their endless failed "counter offensives" and retreats, even if they were motivated to leave no one behind they generally do not have that option as they continuously lose ground. Furthermore their reported loss numbers vacillate between high and low figures depending on whether they are begging for arms or sympathy on the day. They've had to go up to hundreds or even a thousand a day at times as reality becomes harder to hide. In recent clashes its reported they are outgunned by something like 48:1 for artillery, the loses must be extreme.
Furthermore extrapolating the heavily fortified Donbass to the rest of the Ukraine is simply not on, they send men there because the open land behind it is not defensible land.