Balgruuf is an honourable man and a great leader IMO.
He places his people above all other internal or external concerns and in so doing places himself on the path of service to the lowliest citizen of Whiterun. I remember placing my CAPS LOCK on (PC) so that my character would walk slowly from Breezehome to Dragonsreach as I had thought about the possible consequences of his refusal to join Ulfric. I walked back to my home in the same manner after his refusal. My character, devastated.
I found his betrayal one of the hardest things to do in the SC-CW questline. I found the destruction of Whiterun one of the most distressing aspects of the game. It is my home after all. WIth Hearthfire DLC installed and the Battle for Whiterun completed, my adopted children beg me to "Make it Stop". I cannot. I am powerless to stop the juggernaut or change the course of events.
I think if Balgruuf had sided with Ulfric, then joining the Stormcloaks would have been easier for me personally.
So I think kudos to the Beth writers for not giving the player the easy or convenient option. And not necessarily the right option either.