these are my 2c.
1) ssd's have limited writing cycles;
2) even if os x, by default, writes the ram content to the hard drive when you put it to sleep, it keeps the ram charged
anyway -from an electrical point of view- so you find your system ready to go once you awake it. in the event your computer drains battery completely, once you connect it to a power source, it reads off of the hard drive the ram contents previously written.
so, to make it short, the battery drains in either case (by default setting and using
smart sleep /
sleep only thing) as in both cases the ram will be powered to keep its content; on a side note, something different happens if you set smart sleep to hibernate
only.
if you wanted to keep your 'sleep mode' to sleep only, you could find it convenient to delete the virtual file used by os x to write the ram content to the hard drive, freeing up some space from your ssd - this file has been created on the first install of os x, i believe, and it has exactly the same size of your ram, obviously.
now, let's say that your laptop is set to sleep only and you run out of battery, either because you don't have the possibility to connect it to a power source or because you want to calibrate your battery (you are required to drain totally** your battery to calibrate it): guess what happens? you loose everything unsaved from your session and the system does a fresh boot as soon as you press the power button, without restoring your last session (it happens because the only source to restore your session was your ram, which lost power).
the best trade off would be keeping the system to sleep only (getting rid of the useless virtual thing file too), while activating the sleep+hibernate mode when you need to calibrate your battery, so you wont shut down your system suddenly. of course, you'd need to delete the file used to write the ram content down to your ssd every time you want to go back to the sleep only mode - well, only of you want to get rid of that unnecessary occupied space anyway.
**please note: i suppose the battery still calibrates correctly even when the system is set to sleep only, hence it totally looses energy => let's not forget that, from what i explained, by default your computer goes to sleep (sleep+hibernate mode) when it finishes juice in the battery and that's the way apple means calibrating the battery.
i am going to further investigate on this subject during the next days, something which i wanted to do sometime ago but i forgot to, lol.
well, the conclusion is that i am not sure which is the best way to set it. it depends.
