What is the best letter to start a hangman game with?

You are given a cell array with all valid N-letter words. Your output should be the letter that has the highest chance of occurring (at least once) within any randomly chosen word in this dictionary.

You can assume that words will always be in all capital letters, and the cell array will always be a row.

Example:

words={'AAA','BED','BEG','BAD'};

You should return letter='B';

note: Letter 'B' occurrs in three different words. Letter 'A', while occurring four times (counting repetitions), only appears in two different words.

Follow-up:

If you are going to be losing hours of sleep over the issue of whether choosing the letter with the highest chance of occurring within any randomly chosen word is actually the best 'simple' strategy in a hangman game, then the next problem in this series - Hangman (strategy) - is for you. Go ahead and test this or a different strategy there, and the contest machinery will score it based on its performance in a series of simulated hangman games.