If you're in the US I would go with Intel, in case you need to use the warranty.
Even though in paper and benchmarks the 660p looks slower, in real word usage you won't see a difference.
Also the addlink S70 doesn't reserve data capacity (overprovisioning) like most units out there.
Overprovisioned space is reserved for background use, so writes can complete faster when multitasking (gaming/video editing). But that that might not even matter for most users.