rip DVD for PMS streaming

[sanju]

Hi Guys,
I am planning to rip and store all my DVDs into PMS server. Just want to know whats best/compatible format to rip DVD on hard disk, in order to stream through PMS (with subtitle support). I am contemplating between two choices .vob or .iso, so if i have to restore DVD in future i will able to do so without any conversion/reconversion loss (or are there any better ways ?).

Thanks,
sanjau.