I have completed Lost Mines of Phandelvar and Hoard of the Dragon Queen, but neither are options in the poll. Currently playing through Out of the Abyss so I can't really say I've played through it yet.
I think it is a combination.Perhaps another reason CoS spikes in use is its a tighter level spread?
I ran my group through Lost Mine and moved on to Hoard of the Dragon Queen afterward. Still going through Hoard, which we started in either August or September of 2015. (Our group can only meet once a month at most, and there have been a few months here and there where we couldn't meet at all.) I kind of feel like I owe it to my players to continue through Rise of Tiamat—especially since one of them just got me the adventure book as a Christmas gift—but I'd really love to move on to something else.
Well, were still slogging away at Tyranny of Dragons that I brought home from Gen Con 2014. Is been an epic campaign and I'm planning on taking the party all the way to level 20 by continuing the fight to the final showdown with the Queen of Dragons on Avernus.
On the first read the campaign was full of holes, but I've "rolled with the punches" and filled in the gaps as we've played and I must say it's been a beautiful thing! I suspect that this type of broad reaching, epic level 1-20 campaign with factions and politics and armies and intrigue and victories and disappointments has a once in a lifetime experience (and I've been playing for 30 years).
What more can I say!