This may have been mentioned already, but Jenny's is more of a traditional chocolate cake (made from scratch) while AhhhBee's is a regular brownie. I can't speak to AhhhBee's but the potency of Jenny's cake is very high, even if you are an everyday smoker (I believe it's effect on you has more to do with your weight, then if you are a frequent consumer). I think 1/4 should be enough for anyone, if you are drinking an smoking along with it.

My wife ate more than 1/2 one time and she was convinced there was some Obeah magic in that cake.