A hamster bowl is all you need, really - combined with a water bottle, these two pieces of equipment are the food and water essentials for your pet’s cage.
If a dispenser offers unlimited supplies, your hamster might be tempted to store lots of food. Not good.
Pet food dispensers usually have far more food available than your hamster needs. This means the hamster can collect food all day, like a never-ending Eat-All-You-Like Buffet, and you'll whizz through your food supply quicker than you'd anticipated. It's all down to instinct - hamsters stash food all around their territory while it's available. In the wild this helps them build up stores for when times are hard.
This simply means that you'll be throwing away old food when you clean the cage, resulting in a lot of waste. However, if you can find a food dispenser that limits the amount of food available daily, this is a perfectly sensible option. Or, simpler still, just provide the correct measure of food each day in their food bowl.