T450s, W550s or T550?

Hi everyone,

I have briefly browsed through their specs but may still want your opinions. It seems to me that the main differences are that:
- W550s comes with NVIDIA K620M and 16 Gb RAM (5 lbs)
- T550 comes with Intel 5500 and 16 Gb RAM (5 lbs)
- T 450s comes with Intel 5500 and 12+8 Gb RAM (3.5 lbs)

I care about:
- performance (to be specific I do some gaming e.g. DDO, and sometimes need to analyze 800 Mb ~ >10 Gb images using ImageJ / ImagePro)
- lower weight has advantages as I may bring...

T450s, W550s or T550?