consumes less juice and is faster.
Let me just clarify.
The spinning mechanical drive will consume less power. At least the laptop 2.5" do.
Faster .. no.. SSD is much much faster drive. But in situation of backup over network there are other factors.
Gigabit speed for ethernet. Processor power in the NAS or Router. Inefficiency of feeding data to USB bus. So the net speed benefit of SSD in this case is zero.
Over network to USB port you have all the above limitations.. first is gigabit ethernet or even worse wireless.. that gives an absolute max speed of around 100MB/s (B is Bytes.. b for bits) In theory it is 1000/8 is 125MB/s but reality is all network protocols have overheads so an average NAS will peak out around 110MB/s but seldom achieve that continuously except with very large files.. with smaller files it takes longer to write the indexes.
With USB there is another limitation so most routers lose a lot of speed cf a NAS which is running disks on SATA bus.
And a router has a processor of limited speed to save power. Most good NAS use a much more powerful processor dedicated to file storage. A router processor has to do router plus file storage duties.
And yes.. spinning drives are mechanical and subject to wear and faults. So they die.. SSD nowadays are very robust but still have wear issues.. not that most home users will ever hit them. Backups are one area large mechanical drives still reign supreme.
A 4TB SSD is very expensive.. most of us cannot afford them.. so you are living in a rarified atmosphere.
