Before they vote I think that people would do well to consider the following qualifier: Do you deep strike aggressively? By this I mean, do you typically try to position your daemons as close as necessary to guarantee an assault the turn after deep striking? Even with icons, which are by no means an economical or even practical solution in many cases, aggressively deep striking has its risks and as I don't believe that there is a correct answer to this question it comes down to a matter of play style.
If you do not consistently deep strike aggressively, then for the points you'll spend on a greater daemon a Bloodthirster is the best choice. He has the same mobility as a Lord of Change, is nearly as durable, and has the potential to cause a great deal more damage when he does assault. In particular, its potential for S 8 attacks makes it an excellent choice as an independent character and/or monstrous creature killer and out of the four greater daemon options, the Bloodthirster stands the best chance of pulling down a landraider.
If you do consistently deep strike aggressively, then a Great Unclean One is a better buy. Cheap and staggeringly durable as only one in four wounds from a AP 3 or worse weapon will actually stick, the Great Unclean One often takes more firepower to put down than a landraider. Sure its slow and spiteful so when you need to roll a three to assault you will almost certainly get a two but the threat it poses, due mainly to S 6 coupled with noxious touch, can not be ignored provided it starts about six inches from your opponent's battle line.