I had a 05 S2R 800 for 3 years, used it primarily as a commuter bike but rode weekends too. Sold it for an 07 MTS 1100. No regrets, not even for one second.
The MTS is a far more versatile and comfortable bike than the Monster. The MTS wins also for passenger comfort over the Monster.
I suggest you ...

I would go for the Spark exhaust. I had Spark CF cans and full system on my Monster. Excellent system. Very good quality and sounded very deep in tone. Many sound clips available on YouTube to listen to.
On my MTS I have the Remus CF cans. I just like the CF over the bling of stainless. Hope that ...

Jazz:
Congrats! I know you'll enjoy it.
What won your heart the most?