I have a large givi top box and a pair of small panniers but I'm not sure what the best option is. I favour the security of the cases but prefer the versility of the bag.
I will have a tent, sleeping bag and roll mat/ air bed to attach to the bike also and think it'll be easier to attach it to the rear carrier if there's just a bag there.

I have plenty of time to ponder as I don't plan to go any distance until next May!