Something else to consider is change in gear inch when looking at the same cassett. If you compare the jump between cogs at the same relative gear inchs between the 39 and 53 (34 and 50) you will notice that there is a bigger jump when on the bigger ring. That is one reason that I do not like to run on my 39 ring - one shift on the cog is too little, and 2 is too large. One shift on the 53 is comfortable (for me)