Expect the Sensei I have used/experience all of the mouse you listed so I can give you some personal usage feedback among the mouse
The choice is up to your preference, type and usage.

Logitech G9X
> Claw Type Mouse
> Matte Plastic Body
> Adjustable Weight
> Interchangeable Grip (Soft Rubberized Grip / Durable Texture Grip)
> Smallest among the mouse you listed but tend to be a little heavy.
> 5 Onboard Memory Profile(each different Profile would able to customize various of colors you want)
> Smooth Scroll Option

Logitech G700
> Palm Type Mouse
> Texture Grip on Side Button Area, Matte Plastic on Top Surface
> 5 Onboard Memory Profile(unlike G9, Profile Change was limited to Yellow Color and it selected in LED Up & Down)
> Wireless/Wired Type (Comes with USB Dongle for Wireless Connect and Micro USB Cable for Wired Operation)
> Most Button among the List
> Smooth Scroll Option

Microsoft Sidewinder X8
> Palm Type Mouse
> Full Matte Plastic Body
> Full-Time Wireless Type (using Magnet for attach/detach towards the round charger/connection dock)
> Mini LCD Display (Able to show DPI Value, Icon of Recording Macro)
> On-The-Fly Macro Recording

Razer Death Adder
> Claw/Palm Type Mouse
> Rubber Grip Top, Glossy Plastic on Side
> Cheapest among the list
> Lightest among the list
 
Steel Series Sensei
> Palm Type
> Metallic Finish Top
> Onboard Custom Profile Settings by using the LCD at the bottom
> 5 Onboard Memory + Awesome Multi-Color Changes on Scroll Wheel and the Back of The Logo in different profile
> Customize-able Logo on the bottom