I purchased the Genesis E-330 three years ago and it came with non-porcelain cast iron grates.
I had GrillGrates that I use on my pellet grills so to eliminate the problem of keeping cast iron grates clean and seasoned I ordered one more GrillGrate for a total of five and replaced the cast iron grates. All were the 20 inch in length size and I cut the length to fit.
The GrillGrates grill better than the original cast iron grates in that I can now grill on medium to medium high and get better results than using the original grates on high. Also, no need to use the sear burner for most meats.
Now as far as does the increase in grill quality equal the increase cost of purchasing 5 GrillGrates well only you can decide that. For me it was easy as I already had four and I am not sure I would have made the conversion if I had not already had absorbed the initial cost of four GrillGrates.
Prior to using GrillGrates I never had a problem with flare-ups except when our grandson put two much oil on the burgers and still the flareup wasn't that bad and went out on it's own.
As was mention before I also recommend you use the Genesis for awhile and get to know how well the grill works.