There are a few main designs to choose from, each of which should match your goals.
One bottle vs. multiple bottles
A key consideration is how many bottles the holder can store. Many styles were made for only one bottle in mind. Others have compartments to hold two, three or more bottles. If you tend to only take one bottle out for a picnic, the one-bottle design can be easier to carry and provide a snugger fit and tighter insulation. However, if you take multiple bottles to a party, opt for a design that can hold multiple bottles, ideally separated by compartments so the bottles don't bang into each other.
Compartments for additional food and tools
It also common to find additional pouches in wine carriers and totes that can hold wine accessories or other food. For instance, some totes even come with glasses, a corkscrew, a cheese knife and a cutting board. If you tend to take food with you or want additional accessories, compartments are great options. They work especially well if you plan on eating out at a picnic.
Sizes vary based on how much you want to hold. A larger bag style could be about 13 inches high by 10 inches wide by 5 inches deep.
Bar carriers
A bar carrier is usually shaped like a box and has a compartment for wine and a place to put ice. It can often also store bar accessories like tongs. The dimensions on a bar carrier could be around 13 inches wide by 9 inches deep by 14 inches high.