The Cards total offer to Renteria was only $1 mil less in total than the Sox offer.
Renteria left because the Cardinals only matched the Sox's offers as they increased their deals. He wanted the Cards to put their max offer on the table up front. He refused to understand the financial position the Cards were in. Frankly, the fact that the Cards even tried to match the Sox offers is proof to me that they really wanted him. $11mil/season is a lot to be paying a career .280 BA hitter anywhere - but especially so in St. Louis.
Comfort was not a factor in Renteria's decision. Either way that he goes, he has a team with a rich, deep history, a great fan base, and the potential to win it all again next year. Four games in the WS did not change his mind. His pride was what changed his mind. Renteria went back to Columbia, and he waited to see who would stroke his ego the most. The Sox did, and the Cards didn't. So now he's in Beantown.