I have a whole book on the Thera eruption, and they clearly favor the 1646-1626 figures. Apparently it had serious eruptions that scared all the people away and then 2 decades later blew its top.
I know that historians favor 1500 BC because of the decline of the Minoan civilization, but I wonder if that could have been caused by the very major eruption of Etna which took place 1500 BC, +- 50 years. I wish I could find more about that eruption.
Neither date works for the original claim that Minoan civ croaked on raining ash, tsunamis, or whatever else is dreamed up about this. There’s no evidence for any large eruption at either time, so I guess that figures.
http://www.freerepublic.com/focus/f-chat/1180724/posts?page=37#37
http://projectsx.dartmouth.edu/classics/history/bronze_age/lessons/les/17.html
“the wave of destructions (most of them including fires) which defines the end of the Neopalatial period on Crete and to which the palaces at Mallia, Phaistos, and Zakro all fell victim cannot be dated earlier than LM IB (ca. 1480/1470 B.C.?). Hood [TAW I (1978) 681-690] claims that clear evidence of the earthquake which so severely damaged Akrotiri before the town was buried is to be found at several sites on Crete where it is clearly dated to LM IA. More importantly, tephra from the later eruption of the Theran volcano has been found within the past decade in LM IA contexts on Rhodes (at Trianda) and Melos (at Phylakopi) as well as on Crete itself, ample confirmation that the eruption preceded the LM IB destruction horizon on Crete by a significant amount of time. Thus no direct correlation can be established between the Santorini volcano and the collapse of Neopalatial Minoan civilization.”