SegWit has a lot of pros. The lower size (and the associated tx fee) of segwit transactions is probably the most incentive for most users.
But SegWit softfork was the first step towards hashed timelock contracts [1]. The lightning network is one implementation of HTLC's.
Additionally, thanks to the 'block size' getting increased efficiently, this will open doors for better scaling during mass adoption.
Those are a few huge pros IMO.

I dont think there are noteworthy contra arguments to segwit at this time. SegWit is a crucial part of the evolving technology bitcoin delivers.


[1] https://en.bitcoin.it/wiki/Hashed_Timelock_Contracts