"What advertising you guys are talking about in this internet time ? Both agents are going to take pictures of the house, put a board outside and list it in the local MLS. The listing automatically appears on other websites using IDX. "
Are both agents members of Realtor.com? That's the largest, most visited site for home-hunters. Membership in Realtor.com costs thousands per year. Membership is important, because without it, while your listing will appear on Realtor.com your agent won't be able to modify the listing, or add photos with a membership.
Yes, both agents will likely take photos. Will they take good ones, or will they just use that crappy little 4-year old digital that they got for their birthday? It costs money to hire a professional photographer. Will they lighten, crop and sharpen the photos.. Photoshop costs money too.
Will both agents do virtual tours? Those cost money. Will both agents create color brochures as leave-behinds for agents and viewers at your home? Will they produce those same color brochures, and send them out the 100 top agents in your region who have sold homes like yours in the last 6 months?
Will they run any print ads? Will then send out direct mail-post cards... (Just Listed, Now Open) to the 100, 300, 500 nearest properties in the area? Will they conduct broker's tours... when they do will they entice other agents by offering food, or starbucks cards, or gas cards to get them in the door? Will they conduct Open Houses?
Will they advertise on other internet sites... (coldwellbanker.com, coldwellbankeronline.com, CNN.com, Truila, Zillow, Openhouses.com) while some of those are free, or relatively free they take time and effort, and that can mean money. IDX doesn't cover all of them... and sometimes when it does, it takes the bare minimum, and can't be modified (ie: 3br/1.1bath ranch $235,000).
There are plenty of other avenues to advertise, both on the internet and elsewhere that hopefully will bring more eyeballs to your listing. Interview agents, and see what they bring to the table. If you don't agree that they offer an advantage over a lower commission agent, then by all means use the lower commission agent. You'd be a fool not to.
But don't be myopic and look solely at the commission. Consider the entire package, and then make an educated decision.