Do I trust DDNS? No. I'm always skeptical of other people services like this. If the client is willing to pay for the configuration and appliances, and deal with connecting via a VPN from their smartphone. I prefer to use VPN. Not everyone is willing to do this so we have them sign our contract releasing us from any problems that could arise out of using DDNS.
Do I trust cloud? Depends on who does it. DMP has an offering that I trust, I know the people who have built it and they're good people who actually care. I don't trust Hikvision cloud connect and won't use it. NX Witness is about to release V3 that has a cloud connection that doesn't require port forwarding. I'm using their beta right now and it works really well and is easy to setup. I'm not totally sure I trust them yet, I don't know them well but I don't not trust them either. We will see.
I think cloud connect is the future. Port forwarding is no good, setting up VPN appliances or software can be annoying and cumbersome/expensive for customers. It's important to make sure the cloud connection uses appropriate encryption for traffic and login.