MrAce, on 2014-June-23, 09:10, said:
As Helene says the number of trumps + purity + void vs vulnerability.
I just made up this hand. You can make 4♥ (probably +1 ) and the fate of 2♦ doubled depends on very good defense. If you are that good in defense you can set them i guess. Otoh change some spot cards then double may be the winner, The reason for people bidding here instead of double is probably to avoid a random result. At least that was my intention when I voted for 2♠
I think many Easts would open this 1D anyway so as to be able to show both minor suits with less than reversing values. This would certainly be so in all partnerships of which I have been a part, certainly if 3145 in shape.