Greetings.
I am the Collections Manager at the March Field Air Museum and I set up CollectiveAccess for my museum. I used PastPerfect at another museum and did not like it; I prefer the workflow of CollectiveAccess.
I used PastPerfect when I was volunteering at another museum and it felt clunky. CollectiveAccess allows for much more customization of the program, so that you can create a database that does exactly what you need. For instance, we started with a basic DublinCore installation profile, but you can also install the version to match VRA Core, Darwin Core and other standards. Metadata Standards available in CollectiveAccess installation profiles. I have modified the basic installation profile to include elements from the old Access database that did not match up with the new database. Other elements which I like is that the program is a website which means that I can have anyone use any computer connected to our network to access the database. Which can come in handy if someone needs to use a speech to text program.
While I know the people over at PastPerfect are working on this, the current PastPerfect is built on a database program which has not been updated in ten years. The next version will use a different database backbone, so I would suggest that anyone looking into PastPerfect now budget out the funds for the upgrade or to wait.
One of the problems with CollectiveAccess is that the program is a website and is built on several other programs which also need to be running, e.g. Apache, PHP, MySQL, which makes installation a bit more complicated.
Hopefully that answers your questions.