Top-freezer
Its benefits:
Energy-efficient -- The US Department of Energy says that these refrigerators consume 20% to 25% less energy than the bottom freezers.
Affordable -- It's cheaper than bottom freezer
It offers more usable interior space
Bottom freezer
The contemporary mini fridges use this type of freezers because:
More organized, with shelves and baskets as in-built facilities
Larger shelf space, which makes it easy to store larger perishables such as unsliced turkey or pizza.
Refrigeration compartment at eye-level -- Since the freezer moves down, you have this section at a more accessible and comfortable level. Consumer research shows that a bottom freezer also helps users to remember to use veggies in time before they become stale, since they are at eye-level and hence you don't forget to use them.