Same genre, very different games.
Elite D in current iteration is finished spacefaring grindathlon. Going into third season, still very bare-bonesy. Many promised features missing.
Star C is unfinished, early alpha test bed. Real meat of the game should come in 4-5 months, possibly in broken state. Will be somewhat playable sometimes next spring. This is semi negative outlook on things based on experience.
Finished, Star Citizen is better overall game and adventure. Elite will always be broader game revolving around grind.