Samsung s3 is better than Sony xperia s. barometer is not available in xperia s. maximum standby time for xperia s is 450 hours, but for Samsung s3 maximum standby time is 830 hours. but i like xperia s for its stylish package and camera quality.
The Samsung S3 is better due to its superior technology. The Sony Xperia S has a better resolution and it is also cheaper than the Samsung S3. The Sony Xperia S uses TFT technology for display while the Samsung S3 uses Super AMOLED technology.
It depends on what you like. I much prefer Samsung's TouchWiz interface to Sony's more stock Android, and it also has other features that the Sony doesn't have. But it's all up to preference in design and all that as well.