It is much faster to blow away your OS partition in the event of corruption, or you just want to do a clean install.
If you have both data + OS, then you can't just do a clean install.
Well doesn't your C-drive store your profile as well? Documents, videos, pictures, firefox profile, etc. You want that backed up before 'blowing away' the system partition. Storing this data on HDD defeats the purpose of the SSD. Though you can use junctions (symlinks) to store the profile on another partition of the SSD i guess.
It boils down to personal preference. But many people do not re-install windows every week, so waiting perhaps 10 minutes before the SSD is backed up to HDD is not a big deal i guess?
And if this is the case, you can always just move/shrink/grow partitions as needed.
Grow & shrink is just fine, but moving partitions means you need to rewrite all that data and causes write cycles. Besides that, it can be a hassle for users.
I find it much easier, and faster to be able to backup individual partitions when I want, instead of doing the whole thing at once.
Perfectly valid argument - but as you indicate this is pretty much a personal preference. Generally one big C-partition is just more convenient for many and doesn't come with much disadvantages. I think this generally is the best advice, besides power users who have their personal preferences; like yourself.
Yeah, not really a issue for most all consumers, all SSDs are already overprovisioned, and setting aside some more space will only benefit a very small number of very heavy users that write a ton of data to the SSD.
It varies per SSD; the built-in spare space is often included in the 6,7% difference in GB versus GiB. This space is shared with mapping tables, spare pages and the RAID5 parity bitcorrection (1:128). So the amount of spare space is very low. Overprovisioning will certainly help if there is no TRIM or the workload requires more erase blocks being available - such as when using the SSD for caching (L2ARC for ZFS or Intel SRT caching). Also when using the SSD for virtual machine images you really want to overprovision.
For normal consumer usage which has TRIM available, i agree that overprovisioning is not necessary. I've got a chart which shows the influence of spare space on write amplification. It starts with 0.1 (10%) spare space but that is already way above the default of modern SSDs:
Static data is data that doesn't get rewritten so it does not cause erase block fragmentation. Dynamic data gets rewritten/updated often and thus is more demanding for the SSD.
Typical consumer/desktop usage may only be 30% dynamic data or even less; more demanding tasks like L2ARC/SRT caching are like 90% and thus require more overprovisioning to prevent performance degradation and reduced lifespan due to increased write amplification - it will burn more quickly through its write cycles.
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