Personally, i will wait till the PS3 version has some more details.
This is because i wonder if SE will include a HDD (hard drive) in the PS3 game package like they did with FFXI.
Many have their PS3 HDD filled with other stuff and SE might want to keep their MMO independently or in other words just a dedicated hard drive which always works best.
Also, regardless if a shared or dedicated HDD will be used, obviously a preparation of the HDD will be needed because the PS3 uses a FAT32 format and the game will be larger than 4GBs.
So a partition will have to be made and i doubt it will be a partial install meaning the rest of the game will be streamed from the disk.
I doubt the game details will state something like at least 1GB of space is mandatory to play the game.
I would just wait till theres more information on the HDD space requirements and if it comes with it's own HHD then that would be best.
To my understanding FAT32 prevents any single file being over 4gigs. FFXIV will not install as an ISO (single file) on your PS3 HD. It will install as multiple files (thousands) ranging from a few KBs to tens of MBs. Expect FFXIV to install ~20-25 gigs total. You can't really compare WoW and FFXI and LoTRo since those are honsetly low def games. Take a look at HD games like AoC which installs ~24 gigs on a PC.
We are talking about HI-Res textures and scprited voice acting. All of which demand lots of HD space. In the future (years) with expansions and add ons. expect FFXIV to top out ~30-40 gigs total. (assets are borrowed from previous data to cut down on space)
SE won't ship a HD with the game simple because every PS3 sold came with at least a 20 gig HD. They can also state that a larger HD is required to play or that an upgrade maybe needed in the future to expand your hobby.