DLive was the first decentralized video live streaming platform built on top of the Steem blockchain. You could say that it was the "Twitch platform" of Steem as most content posted there are livestreams that includes but not limited to gaming, travel, art and vlogs.
Because of how the Steem community showed interest on their platform and how DLive showed potential for months, the Steemit Inc team delegated around 2 Million Steem Power to them for the purpose of curating some contents(videos) published via their platform. This made DLive one of the top 5 platforms on Steem for months until last week when they announced that they will be moving from the Steem Blockchain to the LINO Blockchain.
As expected a lot of Steem users were disappointed by this sudden move of DLive. I for one think that they just used Steem to start a solid community and earn some funds to start their own blockchain. Grr
Anyways, DTube can be seen as the "Youtube" of Steem. Like Youtube it is mostly used for vlogging and uploading videos. They also do have livestreaming which right now is not that popular with their users (don't know why). Unlike DLive though, Dtube take a 25% cut on your potential payout which honestly is a lot for me and why I preferred DLive months ago.
So yeah the difference right now is that DLive is now on LINO blockchain and DTube is a video social media platform built on top of Steem.
Dlive used to be on the Steem blockchain, but now they moved to the Lino blockchain. While on Steem and Dtube every user can upvote your video which will give you rewards, the only way to earn money on lino is if someone sends you a tip (like on twitch)