Thanks. I'll probably end up creating an unprovisioned partition. It's frustrating, exactly because of the uncertainty re future performance. Especially given the price premium for pro/enterprise level hardware.
You can research if the firmware understands MBR and GPT - if it only understands one, then you have to use that. Alternatively use Samsungs own software (I think it's called Magician, can't remember exactly), it will make sure you have the unprovisioned space setup correctly.