S3 vs. REST performance

I am evaluating use of S3 vs. REST to interface to ATMOS and see a significant differences. The S3 API uses jets3t and HTTPS. The REST API uses HTTP.

1000 files (all 100 bytes each) archived onto the same EMC ATMOS via:

S3:      1061 MS per file

REST:  179 MS per file

Is that expected? Has anyone experienced a different performance and/or has suggestions for improvements?