If it were me, I would skip both of these and instead give Eicosaderm - which is fish oil w/ vitamin E. Both of the supps you mention are fairly good, but they both contain flax which is a grain derivative (some dogs cannot convert flax - so not only do they get NO benefit from the Omegas, they then also get the itchies from the grain). Show Stopper also contains a whole lot of other stuff that could be potential allergens as well, so you just never know what you're getting into there.
If you're looking for skin/fur benefits and Essential Fatty Acids - go simple/clean/pure - and stick w/ a fish oil and vitamin - that's my vote!
Btw, you can get Eicosaderm at vetamerica.com.