I've read that 430 will corrode over time, whereas 304 basically won't. If I'm spending this much, I basically want a guarantee that I won't have to buy another grill for at least 10-15 years -- that's why the ones with the higher grade steel and 25 year warranty were appealing.

I agree that for true barbecue you need to use a smoker, and I'm not deluding myself into thinking the smoker boxes that you can use with some gas grills are going to do the job. However, my typical use case for my grill is throwing some steaks, burgers, hot dogs, and veggies on and wanting results in 10-15 minutes instead of 12 hours.

My current grill handles this job fine, but it's old and rusty and falling apart. I have to keep it outside year round since we don't have any extra room in the garage, though I do keep it covered. My hope is that I can spend a bit more now and not have to send one off to the landfill in 3-5 years.