Big surfaces move big air
A tractor paint booth handles large surfaces, so at the same face velocity it moves considerably more air than a small booth, over a larger cross-section and against heavier filter loading. The blower has to be sized to that airflow and the loaded-filter static together, with margin. Under-sizing a large booth shows as uneven coating as face velocity sags; the recommendation is a high-pressure centrifugal picked for the booth's real, loaded operating point rather than a nominal figure.