How much heat comes from the front of a cob led

Just trying to work out a design here and ideally would like to know roughly how much heat comes out of the front of a cob led compared to the back. If there is data with or without a typical lense the better. Am looking for a front to back ratio as it's something I have just thought about and can't find any info after googling. I understand that most of the heat is directed to the back/rear and assuming a active heatsink is being used to draw as much heat away as possible. Just for kicks say a 50w cob compared to a 100w, I would imagine 2 50w would be easier to draw the heat away from the front. Regards