I'm talking about in all the worlds, not just Dark Ages.
Sun shroom: Produces 25 sun, then 50 sun after about 10 seconds, then 75 sun for the rest of the level. Only costs 25 sun. Plant food effect: Gives 225 sun and produces 75 sun after that.
Sunflower: Produces 50 sun always. Costs 50 sun, which is more then a sun-shroom. Plant food effect: Gives 150 sun.