I don't have experience with either. My brother-in-law, recently went from a cart Weber Summit to a island with new stainless grill. I was the first to cook on his new grill, I had used his Weber Summit and I am a Weber grill owner too. The new island grill was a lousy replacement. I was fighting flareups continuously, heating was not even, and clean-up was going to be real chore.
For me I would compare:
• Flare up control, which grill can I do chicken and steaks without having to worry the meat catching on fire?
• Even heating, which grill is designed to provide the most even heat front to back and side to side?
• Clean up, which is easier to clean up and maintain?
• Durability, is it USA made or China made, how heavy the stainless, the grates, the parts, etc, which will give you the best long term service?
• Features, honestly if I got the first four points in one grill, extra features just don't matter, basic cooking is what most of us do, but if all things are equal on the first 4 points then features are an issue.
• Parts availability, my weber is over 10 years old, I have replaced the grates, flavorizor bars, ignitor, burner tubes, some things I have replaced twice, but I always can get the parts, and my grill is good for another 10 years.