Alternatives are great... All 3 platforms that you have explained have their good sides and bad sides, but I like all 3 more than YouTube :)
LBRY has the best "story", and I think that they have the best way of video hosting (torrent way), and in most of the cases it works ok... The only problem is their LBRY blockchain that has sometimes big time gaps between blocks... (that's the "waiting for confirmation" message after you upload your video)... I think that problem is that their blockchain is PoW, and there are not too much miners because of not that good price of the token...
3Speak is my favorite as I respect their engagement model with different communities and their commitment to Hive...
D.Tube... huh... I have mixed feelings... I like the idea, separate blockchain, etc... but I think that they have made a lot of mistakes with "communication" and lack of punctuality (their mainnet is late 1-2 years, or more)... But, all this can be solved, and I hope that they will do it... Would like to see them on the top...
Cheers!