The size of the refrigerator is obviously first determined by the space you have available and secondly by your requirements. You are hardly going to put a 200 cu ft. refrigerator in a hotel room only used for refreshments.
If you only have a narrow space, the model type you choose may give you more refrigerator capacity.

Refrigerator Model

There are several models available today:

Side-by-side model
Top-freezer or bottom-freezer unit
French door model (side-by-side refrigerator on top, single-door freezer on bottom)
Drawers or Door compartments – my own refrigerator has an upper door compartment, a middle vegetable/fruit drawer and lower freezer drawer.

Side By Side Refrigerators

In general, side-by-side refrigerators are more expensive, with features like through-the-door ice/water dispensers and wine racks.

Side-by-side refrigerators need less door clearance so are great for a narrow kitchen.

Disadvantages or side-by-side refrigerators include higher cost, often twice that of comparable top-freezer models, narrow shelves often don't accommodate common items, and their through-the-door dispensers can be problematic.

Advantages of the side-by-side configuration include: they equire less clearance to open a door, most have ice and water dispensers.

Top-Freezer Refrigerators

These refrigerators are generally more energy efficient than side-by-sides.They are also less expensive. This may account for why top-freezer refrigerators account for 50% of refrigerators sold.

Kenmore models prove a popular choice, according to reviews. The cheaper models in the line have basic features, including shelves with spill guards, gallon-jug storage on the door, factory-installed icemakers and clear crisper drawers.

Popular brands of Top Freezer Models are: Kenmore, GE and Mytag.

Bottom-Freezer Refrigerators

Bottom-freezer refrigerators grown in popularity allowing easier access to the refrigerators, with the freezer often modelling as a convenient pullout drawer
Top rated bottom freezer refrigerators include: Amana, including those branded GE and Kenmore. Maytag has now bought out Amana and has branded a few of Amana's bottom-freezer models as Maytags.

French-Door Refrigerators

These are a combination of a side-by-side refrigerator with a lower single pullout freezer drawer.
Top rated French door refrigerators include: LG get the highest ratings in reviews for energy efficiency and consistent temperature performance. They are also the quietest models, making significantly less noise than GE, Kenmore or Maytag French-door refrigerators.

Built-In Refrigerator

These are designed to sit nearly flush with standard cabinets and can be disguised with cabinetry panel fronts. The custom look gives clean lines to your kitchen but come at a prices. Check out the repair rates and depth of cabinets as these are common problem areas with these models.
An alternative is to get a custom built-in mimic version from credible refrigerator manufacturers as Kenmore, Frigidaire and Whirlpool. These are designed specifically to fit into your kitchen cabinetry. The GE Profile or GE Custom Style series get good reviews.

Styling

Kitchens have gained more focus in design and styling in recent years as the pace of life hastens and everyday tasks such as cooking are doubling as social times in the home.
Kenmore Elite top-freezer refrigerators have sleeker contoured doors and offer stainless steel high-tech looks of designer kitchens. On most models, a stainless steel option will cost you an extra $200 or so.

Ice and Water Dispensers

Kenmore side-by-sides are most frequently top-rated. They are energy efficient, maintain even temperatures, and are among the quietest refrigerator models. These refrigerators range in size from 20 to 26 cubic feet

Reliability

The most reliable refrigerators are Whirlpool, Kenmore and GE side-by-side refrigerators by only slight margins.

GE refrigerators have a lower rate of repair than many and perform consistently well for temperature accuracy, energy consumption, noise and ease of use.

Although Maytags performance ranks with other refrigerators, its appears the least reliable in non-icemaker versions, according to owner surveys. [25% needed repair]

Overall Top 5

Kenmore
General Electric – highest top freezer model
Amana – highest bottom freezer model
LG Electronics – best French door model
Viking – one of the top custom built in look refrigerators

What To Look For In A Refrigerator

Layout – is it convenient for all members of the family
Sufficient width and depth for the common items you refrigerate
Adjustable shelves
Easy to reach controls – many are on the back wall which is not ideal
Independent controls for each compartment
Water filters for the icemaker.
Energy-Star compliant.
Spill guards
Lighting – including vegetable bins and freezers
Noise level – look for insulation around the compressor, especially if the refrigerator backs onto a bedroom wall
Rate of Repair
Duration and Terms of Warranty

Energy Star Rating

Energy-Star rated appliances ensure your refrigerator is energy efficient and attract rebates from many municipalities and utility companies, such as those in parts of California who can claim a $100 rebate when replacing their old refrigerator with a new Energy Star Rated refrigerator. Check with your local utility company for Energy-Star rebate programs.