Delivery I believe I think they prioritise the parcel so they take more care with it, and also it should get to you before noon I think that's right, hard to see properly on my phone
PCS will always pack ya pc properly regardless of the delivery choice you make.
I believe that the diamond delivery is ensure that the package is delivered on time or for a good time pre noon. I honestly think all parcels should be treated the same regardless of how much money is paid. Especially if it say's "fragile" all over it.
Personally i'd just stick to the normally delivery, as its gonna get delivered the same day anyway, and you may pay for more, when it was gonna come around the same time anyway.