Each SP 'owns' a set of LUNs, and a LUN is only active on one SP at a time. (for Clariion anyway)
Really, this makes sure that SP resources (cpu, memory and cache) are used appropriately.
Therefore if you only gather a single SP's collects, you're not going to get all the logs/captures and info about the LUN's the other SP has active on it, and you won't be getting the full picture.
When you look at a LUN's properties you will see the Current owner and the Default owner. When a LUN is not on it's default owner, it's 'trespassed'. In the event of an SP failure, all LUNs on the failed SP would trespass to the peer/surviving SP.
You may also see 'Allocation Owner', which for Pools, manages the slice allocation.
Ideally you want the allocation owner, the default owner, and the current owner to all the the same SP.
I've digressed a bit from your question, but hope the info helps.