I need to replace the heat shields on my Gas Grill. My grill uses
individual "tents" over each of the 3 burners. The ones I am replacing
were porcelain coated but are now beginning to rust out.

I can get 3 porcelain coated heat plates for $43 or 3 stainless steel
plates for $19 - less than half the cost of porcelain coated.

Question 1: Will porcelain coated last twice as long as plain stainless
steel? Neither choice lists the gauge of the heat shields so I can't use
that to compare the two choices.

Question 2: I've seen some opinions that a rock plate is better for heat
distribution than heat shields. That makes sense. However, I assume I
will need a grate to hold the rock plate. A quick search showed some
galvanized steel rock grates. Can I expect these to rust out just like
the heat shields? Buying a rock grate and a rock plate is going to be
more expensive than the heat shields, but if they work better and last
longer, I wouldn't mind spending the extra money.

Opinions sought!