I think from NetApp storage side, whether it is THICK or THIN it has no bearing on storage performance (THICK simply ensures the Volume is given it's 'space' up front logically that's it or literally just for accounting purpose) it's all simply virtualized. Therefore, from Storage Performance point-of-view there is absolutely no difference. However, what it may be trying to say is that - THIN brings 'Storage efficiency' . Just like SERVER side resources such as CPU/Memory/Network can be "oversubscribed", in the same manner Storage side resources can be oversubscribed using THIN provisioning on the basis of the understanding that no system can run at 100% at all time.
However, with THIN you have to ensure (keep an eye) the underline aggregate has enough free space to cater to mission ctirical databases that cannot afford to go offline.