If a professional school requires or strongly prefers a committee letter of recommendation, and your undergraduate institution offers an HPAC service, it is very important and will greatly support your application. The committee letter provides a thorough and objective evaluation of your candidacy for admission to professional programs.
The only professional schools that require or strongly prefer a committee letter of recommendation are medical, dental, optometry, and podiatry schools. Other professional schools do not require the committee letter, and some will not even accept a committee letter.