When you say its better due to the high tensile properties of stainless steel, what are you comparing to? Generally carbon steel has better mechanical properties as compared to stainless steel, though the advantage of SS being inert is a definite plus. Its failure mode is also not as good as CS. There is no such thing as "Grade A" SS in the industry. Try to find out if it is 304, 316, 316L etc. These are the common high grade SSs (corrosion resistance, not strength).
I checked out Fong Yong's doors and from their website, they use the full mortise hinge design on all their doors. If this is true, then it should be a major concern. If they have conceled hinges, then the deal sounds better. Hope there are no 'built-in grills' too...
There are high tensile grades of SS but these are generally considered to be more exotic and I doubt they will be used in door construction. They are generally used for pipes that convey corrosive fluids under high pressures.
Grade A means 304 , grade B 2xx , the composition of Cr is lower than grade A . This is more on corrosion resistance. For comparison if u read my post I'm comparing with newedge/top security 0.9mm zinc plate which they are using. So in terms of tensile strength ss is much more superior.