What are your requirements other than 2 days of dumbells out of the week?
What is your goal? (weight loss, muscle gain, increase performance)
What stage of training are you currently? (beginner, hypertrophy, strength)
Are you looking for a full body work out 3 days a week or split?
Help us out by answering these questions. You really can't go wrong with dumbells as they are capable of working out your entire body while machines limit your "full range of motion" ability.