"not as well rewarded as using DTube" - pretty much, the only reason to use dtube (or 3speak really) is the chance of upvote by dtube or 3speak. I suppose if you produce the kind of content that would get you de-monetized and/or banned by youtube, that would be another reason. BUT (and this is a big but), dtube takes a 10% beneficiary and 3speak takes 11%. In my own experience, dtube curation is terrible - they pretty much only vote the same authors over and over, and unless you are on that list the chance of them finding your video and voting it is almost nonexistent, and meanwhile they will be taking 10% of the votes coming in from everyone else who supports you. Again, that is based on my own experience - but I think it is pretty easily verified by looking at the dtube outgoing vote diversity. 3speak on the other hand has an algorithmic curation that distributes upvotes based on the incoming votes and comments that a post gets - this has its own weakness, as it is pretty easily gamed - but it does make it much more likely that you will get voted.

RE dtube deleting videos - this is the way it has always been. It is in the terms of service. A lot of people don't realize it though, because the POST itself still stays there on the steem blockchain - it is just an empty shell with a video that won't play if you click it. That is why I recommend using the youtube upload method if you do use dtube, because that way at least the post will always have the youtube link even after dtube deletes the video.