at the cartridge itself?  

I had some of both in some mags and I unloaded them.  I wanted to keep the critical duty as the first ones in the mag.  But I forgot to separate them as I took them out.  I think they pretty much look the same....  For some reason I thought I remembered critical defense with a brass shell, but they're all that lighter brass......   Or whatever the lighter case is......  

Anyways...  I wasn't sure if there was something that would differentiate the two that wasn't obvious to me right off the bat.....

I think I noticed one time the sealant  on the primer was different looking.

Not positive though. Could have just been a different lot.

Ive never taken them apart or chronoed them. Not sure if there is an actual difference besides what Hornady says.

Not sure what caliber you have, or if it makes a difference. But I have both in .45 and....

Both cartridges are in nickle cases.

The Critical Duty ammo shows red sealant around the primer
and the tip has an 'H' imprinted on it.

The Critical Defense has no sealant that I can see
and the tip does not have the 'H'.

The Hornady website confirms these visual differences:
Difference between Critical Duty and Critical Defense

It's 9mm and it's a completely different bullet and performs differently.  The Defense is a 115 grain and doesn't penetrate like the Duty does.  Neither is really on the "approved" list.  I think it's because duty doesn't open up that much and penetrates like a madman.  I'm carrying it for winter until I get some better stuff.  Defense maybe underpenetrates a bit.  Some of the tests I see show differently.  Especially from a shorter barrel.  But I had some around so......

I just put all Duty in my gun now because I had an extra box, until I got this sorted out.  LOL.  I need grab some of the approved ammo, but I don't ever see any of it locally and need to order some.

That worked!  I was able to separate the two...  The Critical Duty besides having primer sealant, had a nickel primer.  Whereas the defense had a brass looking primer.  I'm not sure if that's always the case.....

I don't see the H in the polymer tip of the duty though.......

Interesting,
I have Critical Duty and Critical Defense in 9mm, 40S&W and .45ACP.
All have brass primers,
and all the Critical Duty have primer sealant and the 'H' in the tips.

Glad you got them sorted out, though.  

Thanks for your help.  Does your name mean Washburn Guitar?