Poor judgment was Sonny's middle name.

I agree. But there were moments in the movie where he had the right idea. He was the first one to suggest that Sollozzo be killed, but Tom talked him out of it by saying all the Families would come after him. If Michael hadn't said, "We can't wait" on killing Sollozzo, Tom would have still been trying to negotiate.

Tom also erronesouly thought that the Families had stopped fighting because the Families had been quiet when Sonny suggested killing Tattalgia. So even though Tom wasn't as implusive and reckless as Sonny was, he had some lapses in judgement as well that put the family at risk.