Sameerrao,
The 1.7 teleconverter in combo with the 70-200mm 2.8 VR is superb 8)
The 1.4 teleconverter doesn't have as much loss as the 1.7 of course. The reason I went for the 1.7 anyway was because, I geuss you will only use a teleconverter when there is enough light availible to take clear images. When this isn't the case you will get too much loss with the 1.4 as well and you would better shooting without one anyway
Although that there is a possibility that I will purchase the 1.4 as well. But the 1.7 is fine.
Cheers