IPhoto'11 or iPhoto'09 - which way to go?

Question

I have about 30gb of iPhoto Libraries (about a dozen), all in iPhoto6 format (since my photo work was done on the PBG4). I have iLife'09 on all the rest of the family machines, with some 'play' (couple of dozen photos) libraries in the iLife8 format -- IOW, nothing that I need to convert/merge in. All my work will begin from the set of iPhoto6 Libraries (now backed up in multiple ways/places).
My new MBAir (replacing the PB) came with iLife'11. I have a couple of ways to go:
1) convert the iPhoto6 Libraries to iPhoto'11 (iPhoto9) format and
..1a) only use the MBAir for my photo work;
..1b) upgrade all the home machines to iLife'11 (so that any computer can access the photo libraries);
2) install iPhoto'09 (iPhoto8) on the MBAir, and ignore (or uninstall) its iLife'11.
From reading through the threads here, it seems like (2) would be the best course, for now. Opinions?
If I do go with (2), is there any problem getting iPhoto'09 onto the MBA? IOW, can it co-exist with iPhoto'11? (Yes, I understand that the Libraries are Rev-specific but I'm accustomed to launching via the OptionKey to select a particular Library, so that's not a concern.)
FWIW, the Libraries are on an external drive and therefore could be used by any of our machines, so there is a slight advantage to having the same rev. of iPhoto on all.
Finally, I plan to start using iPhoto Library Manager once I have settled on an environment. I assume that it is a fondly-used utility for the iPhoto community -- i.e., have not read any dire reports on its use (but would like to hear, if I've missed something).
Thanks!

Answer 1

Terence Devlin wrote:
No, there is no issue having 11 and 09 on the same machine - just put one into a Folder within the Apps folder. Note that updaters won't find it there.
I have a point of feedback on keeping multiple versions of iPhoto around.
I began processing my multiple Libraries (all in iPhoto8 format) using iPLM. At one point, I used its option to create a new Library and then moved some iP8 photos into it. However, when I tried to open it using iP8 I noticed that it was actually an iP9 Library. I contacted the IPLM author and he gave me this very useful reply. I share it, as other may find this good to know. (I have now 'compressed' my currently-unused copy of iPhoto9 and have not had further difficulties/confusion.)
There isn't really a great way to keep two different versions of iPhoto installed simultaneously. iPLM gets the location of iPhoto itself by querying OS X, which will typically return the highest versioned copy of iPhoto that it finds. If you look in the lower right corner of the main iPLM window, that will show you what version of iPhoto iPLM is using, and clicking the version number will show you the full path to the iPhoto application itself. So when you create new libraries, open libraries, etc., that version is what iPLM will be using.
The technique I typically use to keep multiple versions of iPhoto around (I have every version back to iPhoto 2, since I have to test iPLM with them) is to use the "Compress" command in the Finder to make a .zip version of the iPhoto application, and then delete the application itself. The OS can't use the program while it's zipped up, but then if I want to switch, say, from iPhoto 9 back to iPhoto 8, I just trash iPhoto 9 and unzip a copy of iPhoto 8, so I only ever have one unzipped copy around at a time.