A lot has been written over the years about which is better overall: using free weights (dumbbells, barbells, kettle-bells, etc.) or weight machines? As we age, there are special considerations that can help us best answer the question. A recent article in IDEA Fitness Journal gives a good summary of the issues as well as recommendations.
Free weights have some advantages. If you do not belong to a gym, it is much easier and cost-effective to have dumbbells at home; this is the case with most of my clients. In general, exercises with free weights more closely resemble the kinds of activities we do on a regular basis like picking up bags of groceries, putting boxes on a shelf, or carrying suitcases. Because the machine does not do all the thinking for you, free weights require better form and more coordination. On the one hand that is a good thing because it replicates real life situations, but it can also result in injuries due to poor form or too much weight.
Weight machines also have advantages. Most have instructions right on the side telling you exactly how to do the exercise and what body parts will be affected. As long as you follow the instructions, it is difficult to get hurt on a machine. If you belong to a gym, there will be lots of machines and many opportunities to add more weight to the exercise to increase the degree of difficulty; with free weights, you have to go buy more equipment.
From a fitness standpoint, recent research indicates that both kinds of exercises are effective in different ways. For those looking to increase muscular strength, machines seem to be a bit more beneficial. For those looking to improve functional performance, free weights are better. The truth is that most older adults are looking to do both! As in many things in life, a combination of both is recommended for those who have access to free weights and machines and know how to use both safely. The guidance of a fitness professional can help to ensure that this requirement is met.
Most imporantly, make sure that resistance training is a part of your fitness regimen. Cardio is amazing, but we can raise our fitness and functional levels most when we include weights as part of the program.