What are the measurement differences (case head/ web)in the different brands of the currently produced 6.5/284 brass? I know there are reamers set up for Norma brass. Which brands are the same? Are the Lapua and Norma measurements the same?

Chris,
I don't know how one would get such data except to section a case from each manufacturer and compare.
As far as I know, there is only one company making 6.5/284 brass with that headstamp. That company is Norma. They also make the 6.5/284 brass that Hornaday sells.
Norma brass is excellent and seems to have a large internal capacity compared to other brass.
The .284 case has been wildcatted umpteen jillion ways and is noted for its exceptional strength.
The .284 Win cases from Winchester, when available, can sometimes be a challenge to neck down without collapsing the shoulder.
Hope this helps a little.
Great Shooting
The Bearman

Lapua is also producing great 6.5-284 brass cheaper than Hornady and Norma. The only thing I have noticed with the Norma brass is a slightly thicker neck.