The safeguards there are the same because both have battery isolation and shock isolated bezels.  Both units have the same switching options: momentary tailcap's, clicker t/c's (the Z49/Z59 will match the Classic Tac' light in color) and there are the tapeswitches.  You could even pop on a new XM tailcap.

The Classic series are only 6 & 9 volt systems and though the Classic 6v lamp format is the same as the M95 series the 9v Classic uses the P90/91 lamps which are bit under (105/200 lumens) the M96x series which uses the MN10/11 lamps rated at 125/225 lumens.  As pointed out the Classics are bit lighter and have certain benefits if you have limited mounting room.

The Millenniums of course have the mount solutions included and come with spare lamps.  The 9v series can be switched from std. bezel to turbohead (+ lamp change) or you can do the reverse.  The MU systems will go up to a 12v system.  Last, the MU's just look cool.

Quoted: I have a 6v classic on my aug using a surefire mount on the scope arm. What are my options to upgrade my lighting? I have the tape switch now but it is a PITA. I would love to go with a LED head unit or a 9v unit with LED. SorryOciffer

You can always ditch the tape switch and go to a std. tailcap or clicker style and you'll be able to use a KL3 1 watt LED head.

To convert the system to 9v you'll use an A19 9v conversion adapter and then you can go up to a P90 or P91 lamp, or, you still have the option of using a KL3 1 watt LED head.  Please note the KL3 won't yield distant downrange performance but will give excellent flood for closer ranges.

In 6v mode you can also get the new KL5 5 watt LED head which offers comparable performance to the P60 lamp but be warned, it'll take a while to get and be very expensive.  Battery runtime for the L5/KL5 is also an issue, it will be no greater (& perhaps even less) than a P60 lamp.

BF