We have been using crowdfunding for our own deals since 2014. We sponsored our deals on iFunding.com and then moved to a white label solution that didn’t do everything we wanted. So we ended up building our own platform that we now license to other promoters (realstarter.co).
The marketplaces you mention are very investor friendly and have their interests in mind. Their investor lists are what give them value. A good offering on a crowd funding site can be funded in a few days or hours. The problem from the promoter’s point of view though is that each marketplace has to underwrite and approve your deal. That marketplace is also going to be on title, so they have control over your exit.
From an investor point of view, the marketplaces you mentioned are all very good. From the promoter point of view, you’re probably not likely to get on those sites. Crowdfunding is also really aimed at projects that need to raise between $1M and $5M. Maybe $10M tops. Once you get higher than that, institutional money is much easier to get and organize.
Crowdfunding is still regulated in the US, so for general solicitation, most offerings are going to be 506© which requires the investor to be accredited. You don’t have to be accredited for Title III or Title IV offerings, but those are much more expensive for the promoter, so they aren’t used as often.