You can't compare these two cameras right now.
According to Amazon.com, the SD750 will not be available for purchase until April 15. The SD1000 can be found in some stores now.
My best guess is that the SD750 will be almost identical to the SD600 but with 7 megapixels and the SD1000 will be almost identical to the SD630 but with 7 megapixels.
Here is a review of the Sony T50:
The Sony T100 appears to be identical to the T50 but with a 5X zoom lens and a 3 inch LCD.
I am having trouble on deciding whether I should purchase the Canon SD 750 or the Sony T-50. I would like know which is the better camera of the two. I am also looking at the Sony T-100.