Nothing changes for YouTube; exactly the same content will appear on both platforms at exactly the same time, its just another option for you to view the videos, and it also gives me some peace of mind that the videos are hosted in more than one location.
Importantly, nothing changes for Clickspring Patrons either. I won't be taking up the "early access to content" option offered by Vessel, so Patreon.com/clickspring remains the only place to receive early access to Clickspring videos.
Personally I really like the look of the Vessel site, and the way they deliver content. They have a great attitude to creators, and have been a totally awesome group to deal with thus far, so be sure to check out the platform and see if it fits you too - vessel.com/clickspring