Thats true. I compared SEMrush with Google keyword planer the estimated volume was nearly identical.SEMRUSH generally gets the answers from Google keyword planner and other similar sources.

This makes sense because Ahrefs and SEMRush only give organic traffic, Similarweb includes all traffic. Don't know about Datos.Similarweb is often the best indicator. I have said for a long time Ahrefs seems to be under actual numbers and Semrush is more accurate than Ahrefs.
However I was reading this earlier today;
There was an interesting case study done by Rand at Sparktoro
View attachment 233330
But read the comments at the bottom of the page as to how the Ahrefs numbers were not accurately portrayed.
Case study here; https://sparktoro.com/blog/which-3rd-party-traffic-estimate-best-matches-google-analytics/
I face the same issue when I check traffic for SEO sites.I'm doing comparisons on organic traffics of some websites and there's like 5-6x difference between Similarweb and Semrush. Semrush seems to understate a lot. Anyone else experienced the same?