You will find that seat and head tube angles pretty much will all be within the narrow range of 72 to 74 degrees and will vary even between the sizes of a given model. About the only generalities that I know of is that a more race-oriented bike usually has a steeper--e.g., 73-74 degree--headtube angle and shorter wheelbase (and so, a shorter chainstay length, which sort of dictates a steeper seattube angle. A more comfort-oriented bike oftentimes will have a little longer wheelbase so a more relaxed--e.g., 72-73 degree--seattube angle is possible because a longer chainstay length is not a problem (and may be desirable for larger tires and a wider gear range).