While I was going through my Mag stuff to see what I can let go, I looked at my various valves and was curious about the weight differences. So I grabbed six (which correspond to most valves out there) and measured them. On/offs, power tube tips and spacers were kept intact.
6th place: stainless steel SmartMag
5th place: stainless steel/aluminum ReTro
4th place: stainless steel/aluminum Classic RT
3rd place: stainless steel A.I.R. & Shocktech aluminum
2nd place: aluminum X
1st place: stainless steel A.I.R. & aluminum DeuceMachina cap
11.3oz SS classic
9.9oz SS/aluminum ReTro/E-mag/RT Pro
8.7oz SS/aluminum RT
8.4oz aluminum back SS classic
6.8oz aluminum X-valve
6.2oz aluminum capped SS classic
Yeah, the capped valve will require a secondary regulator so isn't the lightest in operational use, but the change in balance and length is something to consider.
This info may not be that useful...but it is knowledge and something else to add to the database that is AO.