First off, you do not have to trim spare ribs. It is a personal preference. Secondly, yes there is a difference. Spares are larger and have a bit more meat.
Here is a fun experiment. Cook all three styles of rib and see what you like.
I have a Summit S-670 and I am having a problem with just one valve on the manifold. The ignition is weak and the valve itself is a little wonky. I want to replace the valve but Weber service does not sell just the valve. They want to sell me a whole new manifold, valves and ignitors and all for...