I am speaking outside my expertise or training, but I am told an Asherman chest seal may be more appropriate to the random tension pneumothoraxes you would encounter, say, outside battlefield conditions.
My instructors (plural now) and MDinana have said to avoid the Asherman. See
http://forums.equipped.org/ubbthreads.php?ubb=showflat&Number=211911&page=3 .
A US domestic major bleed may be sweaty, but not body armor in 110 degree heat sweaty. There is no petroleum gel, its sterile, and it won't expire in your bag.
Tension pneumothorax usually implies penetrating chest trauma, which in turn implies bleeding. A chest seal that doesn't seal isn't nearly as useful.
I have an Asherman in my kit but no training on treatment of tension pneumothorax, so only a vague idea of when to apply it.
I'd advise you to get training. If you want to PM me with a locale, I could look to see if there was training I could recommend.
Anyone who wants to treat me with decompression needles to my lungs better have the license and certification to do so, that's all I'll say about carrying those.
I wouldn't use one unless that person was going to die without it. I'm much, much more likely to use a purpose-made or field-expedient chest seal, especially if I can expect an ambulance to arrive soon.