The method you choose is up to you. Method 1 tends to under rate the busy hour trafic figures as a peak time on one day may be low traffic for the corresponding hour of another day.
Method 2 overlooks the traffic trend for the rest of the sample. For example a relatively low traffic sample across the period can be masked by one high peak in ttraffic which may be caused by an abnormal event.
I prefer to find the highest daily BH then average them. More precisely, I try to take a long sample period and average the ten busiest hours.
The needs of your client need also be considered, for example would you bother using a Busy Hour calculation to determine trunk/circuit quantity if you were dimensioing an emergency service call centre? more likely you would determine the peak busy hour for a known sample and make sure you over-engineered the route!
Also be aware that BH calculations in this manner may mask actual calling pattern, for instance if all calls come in in the first 10 minutes of the hour sample the overall traffic may seem low, but the client may need to cater for the busy 10 minute period !