Julze -
I have bought the Video Sender Platinum and love it. What I believe to be the difference is:
The Video Sender Platinum has a remote "repeater" built-in. That means that you use your TV remote in the second room to change the cable box in the first room. A nice feature. I find it very handy.
The L2 sender has the USB plug, which, although I never used it, I believe you use with a Mouse Remote. The USB plug hooks to the computer, and the remote moves the mouse on the screen.
I have been a big proponent of the Big Picture Kit, which was available for $19.99. It has a mouse remote (9-pin serial) and VGA connector adapter in the kit. I have previously posted links to the offer for it. That will work with your TV, but will not extend your remote to the second room. It will have a mouse remote if you have a 9-pin serial port on your PC.
I suggest doing what I did - Get the TV Video Sender with universal remote and remote extender
http://www.x10.com/promotions/wireless_video_sender_vk82a.html (generally $49.99),
AND the Big Picture Kit, part of the TV Lover deal here -
http://www.x10.com/promotions/x10_mystery_fun_bags_2.html#tvClick "Whats Included" in your cart to make sure you have the right stuff!