Here’s the scenario: You have website. So does your primary competitor. Most of your customers buy, or at least shop, via the Web. So how should you approach your Web presence? For starters, make sure it works better than your competitor’s.

And by “works better,” I mean it makes it easy for customers to do what they came to do. Period. That’s why we use the Web—to DO stuff.

For this year’s annual beach trip, my family is looking to rent a house on the beach. Having spent many July 4ths in south Myrtle, I had some idea where I wanted to stay. I also know the names of the two big rental shops. Time to get online, right?

Today I checked out the two rental agency sites (let’s call them Rental Company A and Rental Company B), and I’m amazed by the discrepancies. They’re especially perplexing when you realize both sites are built by the same company.

Regardless, here’s the rundown of how Company A trounced Company B in helping me do what I wanted to do:

Company A, Dunes Realty, offers three standout benefits:

1. The search lets me limit price right away, to filter out those houses I couldn’t dream of renting. Not only does that keep me from having house envy, but it limits my choices to a reasonable, and relevant, number. Bonus: The return list includes thumbnails of each house. Nice.

2. From that results page you can “map the listings” through a Google Maps mashup that shows exactly where each house is, more accurately than if you type the street address into Google directly. Combined with the satellite imagery, you can get a great view of each spot.

3. Once I select a listing, it includes multiple photos of the house, and in many cases a floor plan. It’s so easy to post those things (hello, realty intern), and they’re probably one of the most important decision-making tools for renters who buy from hundreds of miles away. “What does the deck look like? Which room has the bunk beds? Where will Dad sleep?”

Those are features I need. That makes them benefits.

Company B, Garden City Realty, trails in what they offer. Maybe they love what they offer—their features. But they don’t help me do what I want. Here’s how it stacks up against the notables from Dunes:

1. The search doesn’t let me limit price, but does asks me to pick an “area,” which ends up being a way to divide up south Myrtle Beach further than I’m familiar with, even as a repeat visitor. How about a map tie-in there, people? Luckily (cough, cough) the return listings don’t show thumbnails, so I’m not taunted by the many listings I can’t afford.

2. There is no mapping of any kind. To get a sense of where any house was located, I had to copy the address, open Google Maps separately, and search it. The best Google could do was get in the general area, not pinpoint the house.

3. Once I selected a listing, there was only a single photo. To see more I have to endure a “virtual tour,” which is essentially a photo slide show, but it loaded—slowly—in a new window. If a picture is worth a thousand words, then viewing these photos was like wading through War and Peace.

In the end, I did spend some time on each site, but easily spent much more at Dunes.com, quickly browsing more options, which is what any business owner wants.

Today’s lesson? When building a site with which customers will interact—which is to say, when building a site—it’s not enough to impress yourself with features of what you offer. It’s more important to start by asking yourself, “What will my visitors need or want to do?”

Functionality, usability, and, most of all, user benefit should be your web-development mantra.

By the way, I’ll be staying oceanfront in a Dunes Realty house over the 4th of July. Give a shout if you’re in Myrtle Beach.