the way that i compare coke and pot is exactly like you said deisel. its like night and day. When i did coke alot for a long time and then started smoking again. i explained it this way:

coke is satans drug....has you goin for a little while makin you feel like its the best thing and then BAM you reach hell cuz you have NO MORE

weed on the other hand is gods....opens up your mind and makes you think about alot of stuff. makes you happy and lasts a hell of alot longer...