The WeWorkRemotely works really well. I've never had such a response from one of our job postings. 50 or so qualified applicants in the first week, and we hired a perfect match out of that pool. In contrast our stack overflow ads had gotten 3 highly unqualified applicants in 30 days.
I haven't tried WeWorkRemotely, but I can attest that StackOverflow ads were abysmal for us. Our final candidate ended up coming to us organically for the position I just hired for, but we also had some good candidates find us from Indeed.com
May have just been the nature of the position though (Salesforce work)
Depends on your ad stackoverflow has gotten the largest bang for the buck with $1200 in spend I've hired 4 members to my team. There are a lot of jobs there so you need to standout but they definitely have good programmers on it. 37s job board was crap for us tho
