Well, from someone who has both, i can say that v3i is easily the better phone overall.
1. more memory w/ tf card
2. better pictures once up'd to your pc.
3. Camera is verrrry laggy on w600, v3i has no lag.
4. iTunes on v3i
5. w600 is probably THE most uncomfortable phone i've ever held in my hands. (bulky)
6. swivel design gets old very very quickly and is nearly impossible to open with one hand on the fly when your driving or doing anything else.
7. w600 screen is tiny. razr's is decent size.
8. SE's headsets are better and music is louder including speakerphone, and this may be the only thing i like about the w600 over v3i, maybe that nad the fact that w600's faceplates are so easily replaceable. Also, music transfers are faster on the w600.
9. SE's headphone and charger inputs are very cheap feeling. when you plug and unplug the phone, its very dissatisfying. (minor, yet very annoying for me)
I will say this, the w600 has cooler camera options like panoramic and burst mode and flash led (although the flash is pretty useless making pictures come out very orangish)... But for most people those features dont mean much when the camera is only 1.3 megapixels. And for some reaosn the screen is very slow when in camera mode. But overall as far as phone functions go, the v3i is far better then the w600 from my experiences. reception is far better on the razr too. The w600 was just too think and short making it uncomfortable to talk with unless the swivel was open. I get reception in my basement no problem while the w600i missed many calls.
10 out of 10 times i would go with the v3i but i guess everyone has their preferences.