I am planning to self host cloud storage for personal use / family members.
As far I think, hard disk drives are more reliable compared to micro sd card.
The new board of bpi comes with micro sd card slot to install OS, but the old M1+ board had sata slot but it is dual core.
So I want to know which board to go with for self hosting purpose ?
This article will help you to understand the limitations and options - so you will not be disappointed.
The M3 and the R1 have a sata port also. Aside from hardware you should consider software support. Question: Would you be satisfied with samba?
I use the M1 with the OpenMediaVault distro and I am happy just using samba. It has a nice admin interface. It has turn-key solutions for OwnCloud and WebDAV among others. OwnCloud is nice but its sluggish for my taste. You can find a beta image for the M3 on http://simplenas.com/download/banana-m3 (should be faster)
Anyways because I found myself happy just using samba I wish I had gotten the R1 because OpenWRT supports samba shares and my router (being 5 years old) is getting very finicky.