omniscienceSneak AttackAlurenbatter skullinkmoth Nexushelm of obedience
just off the top of my head.
i run 4 decay main and still play 3 grip in board. I must admit I haven't tinkered much with board since i made it but I made it at a time when omni was played a lot because dig was still in the format. If sneak and omni are not issues in your meta, then decays should be fine. HOWEVER, krosan grip is G instead of GB making it easier to cast for some manabases. Also, under moon, its easier to get access to 1 color instead of two. Do note that grip does not hit magus of the moon tho.
Additionally, there are times when split second does help more than just being uncountable. For example, when you have to target a sensei's divining top.
So as you can see there are some trade offs. I'm sure there are more but I'm completely fried right now.