Generally .com, .net, .org are considered the Big 3 in terms of domain extensions.
They've been around the longest and all 3 are recognized by the average internet user as trustable.
However....what do you mean by expired .org and put in work?
With PPC and PPA campaigns....expired domains are not necessarily required. You are paying to send the traffic to the website, so whether its a .org, .com, .info etc shouldn't really matter.
If you plan on trying to use the expired .org domain to try and rank it in the search engine results, then yes a good expired .org will work just as good as a good expired .com or .net.