PowerBook - The BEST OS for G3 Pismos and Lombards....

Hello,
So this thread is going to give my dad an idea of what OS to buy for his collection of G3 PowerBooks. He buys them off of ebay for my brothers and for himself and since i'm the Mac person in the house, i'm the one who gets stuck with fixing them and their problems.....yet he doesnt listen to me when i say buy PANTHER......i told him to buy 10.3 Panther, and i made SURE he knew it was 10.3 Panther, we had a long talk about which version of OSX was which animal name. So, the next day I look on his ebay and saw that he bought 10.0.3........great. He said he just bought it because it was only $15 and at least its X and not OS9. I said don't bother installing it, it would only hurt the 'Books because of the lack of DVD playback, but he did anyway. Now 2 of them don't even boot the OS anymore, and as a result I notice a pile of powerbooks with a note outside of my door saying please fix. Great.
I told him again, make sure its PANTHER, 10.3, now I look in his ebay again and he's watching and bidding on JAGUAR.
Irritating! He also neglects to listen to me when i tell him to upgrade RAM, as a result we have 5 unused PowerBook G3s which are very slow, and 2 iMac G3s running tiger daily with a measly 128MB OF RAM!!!!(But don't worry, i'm buying my brother a stick of 512 for his birthday)

So I ask you this, what is the best OS for the G3 Pismos and Lombards, and why?

The specs are

Pismo
768MB Ram and a 40GB hard drive 400mhz(the only one with decent specs...)
Lombards
one 192mb ram and a 12gb hard drive 333mhz
one 256mb ram and a 6gb hard drive
one 512mb ram and a 4gb hard drive
one 384mb ram and a 6gb hard drive.

Most of them have DVD drives.

So, which OS would run best?


Thanks,
Tanner.