Grain absorption

I was wondering what factors should be considered when determining a grain absorption rate. Is there any significant difference in wheat versus barley? If you are brewing 10 gallons of pale ale or 10 gallons hefeweizen, any noticeable difference in water needed? Is this something to consider when it’s on a commercial scale (50-100bbl)?

I’m sure it has to be figured in on a big system, but they have programs to get them close, and if it’s off then adjust it on the next batch. On 5-10 gal. It probably won’t make much difference what grain you use.