If you mean what benefit is there to you personally, perhaps there is none. But, if in a few years you decide to do another playthrough of Sonic games, why not play through enhanced widescreen versions? Especially if the updates are free. Sonic CD looks great in widescreen mode, the other games from that era should too.
By the way, optional Spin Dash has been confirmed, and a Sega executive confirmed that they're planning on remastering other Megadrive games.
segabits.com/blog/2013/03/28/mor ... -confirmed
Bring on remastered versions of the Shining Force games.