Pros: Access to more people and more types of people.
The most obvious benefit of these websites is that they provide easy access to thousands of potential dates.
In addition, when we read vague information about someone, we mentally fill in the blanks with specific details that may be incorrect (Norton & Frost, 2007).
For example, when you read in a man’s profile that he’s a movie buff, you might think that's something you have in common, but when you get to talking about movies on your date you realize that you’re a foreign film aficionado, while he’s obsessed with horror flicks.
It is well documented that physical attractiveness is a major factor in romantic attraction, especially initial attraction (Sprecher, 1989).
For more on misconceptions about online dating, read my post on 4 Myths about Online Dating. More importantly, that they don't see the problem inherent in the dishonest representation is a huge red flag.
The same principle applies to online dating: The sheer number of potential partners creates abundant choice.
So if one dater doesn’t suit the bill, there are hundreds more who could be better.
But this also creates pressure quickly to turn your online connection into something romantic, rather than letting romantic feelings develop more slowly.
When you meet someone in the context of an online dating site, the stage is set to look for an immediate romantic connection— and to abandon the effort if there’s no spark.