When it comes to voice assistants, Amazon Alexa and Google Assistant lead the pack by far. With reports that Alexa may be losing dominance, the competition between the two is only going to get more intense.

CNBC spoke to five ad agencies and who have worked on projects on both devices on behalf of marketers, usually creating branded apps for the voice experience. Here’s the pros and cons they’ve seen for each device.

Alexa everywhere. Alexa has entered far more homes and offices. About two-thirds of U.S. smart speaker enthusiasts will use an Amazon Echo according to eMarketer, with Google Home coming in at just 30 percent.

But Amazon wants Alexa to be in as many devices as possible rather than just its own products, according to Chris Neff, senior director of innovation at advertising agency The Community. Even if Alexa-enabled devices created by Amazon are losing market share, it could continue to gain ground through Alexa partners, he pointed out.

“The biggest strength of Alexa, of Amazon, is right now the market penetration and their goal of getting Alexa into everything and everywhere,” Neff said.

A seamless retail experience. Alexa is tightly integrated into Amazon’s core shopping platform.

“The most expensive ad space in the future will be Alexa,” digital agency Huge global executive creative director for innovation Sophie Kleber said. “They are really just integrated in the shopping platform.”

This has also opened up the door for marketers to sell items through Alexa apps. Vayner Media worked on converting popular mobile game “Heads Up!” for Alexa, and was the first to integrate a voice-activated one time payment functionality to buy add-ons.

“That’s a whole different way to monetize work,” said Patrick Givens, vice president and head of IoT agency VaynerSmart.

A developer ecosystem. A couple agencies also pointed out Amazon has been very open to experimentation, and has invested quite a bit in tools for developers like Amazon Voice Services.

In addition to testing out payments, apps like Gimlet Media’s Chompers – a two-minute podcast to get kids to brush their teeth – has a natural home on Alexa for Kids. An interactive audio story made by Earplay and Universal for “Jurassic World: Fallen Kingdom” lets players dodge dinosaurs using the Amazon Echo’s buttons.

“More developers are coming into the Alexa ecosystem, because they’ve made it easier for developers to create skills and apps,” said Dan Calladine, media and marketing agency Dentsu Aegis’ head of media futures. “What we are starting to see is more creativity in the space.”

Better language processing. For Alexa and Assistant to become real voice assistants, Neff said they’ll need to be able to nuances of how people speak, where they are located, and what they would like based on their past history. For example, it should be able to understand Neff is living in Miami, and based on what he frequents, know not only that he likes Hispanic food but exactly what type of cuisine.

“Now that I’m able to ask these smart devices recommendations, I would want to ask them to tell me something interesting to me,” Neff elaborated. “We’re delving more into it being an assistant and less of it being a transactional device.”

While Alexa has an advantage in e-commerce, agencies say Google Assistant is better at natural language processing thanks to Google’s history of being a search engine. It has a leg up at understanding how people speak and finding them the right answer.

For instance, no one asking someone else to buy them a jar of mayonnaise would describe it by the actual size in ounces, said media agency Mindshare North America chief instigation officer Joe Maceda. Most people would say they want a small, medium or large container.

“That’s something we have to think about: How do consumers think about our products when they are not staring directly at them at a brick and mortar shelf?” Maceda said.

According to research from Dentsu digital agency 360i, Google Assistant is better at comprehending the way people really talk. The team asked 16,000 travel, finance, retail and automotive-related questions to both devices, and found Google Assistant was five times more likely to give a correct answer as Alexa.

“Google obviously plugs into the Google search network, which has all the resources that Google has including all the history of search,” Dentsu’s Calladine said. “It’s why Google has become the most popular desktop search engine. I think that’s the main advantage of the Google Assistant is it’s one its part of the whole Google ecosystem.”

The other divisions could also help Google Assistant progress futher.

“I would potentially say that they are probably neck and neck, but Google has the advantage because of all the deep learning research they do outside of the Google Assistant space that they could tap into,” Huge’s Kleber said.

More experience with developers. Google is also very developer friendly as well. Because of its experience developing a platform through Android, Kleber said Google has experience being the a resource for people and developers. Those skills could translate to helping marketers connect with consumers.

“Amazon is used to pushing their own brand forward,” Kleber said. “Google is used to being a platform for brands.”

In the long run, the competition great news for voice innovation.

“The important thing is as far as consumers are concerned is they both are perfecting the consumer experience,” Mindshare’s Maceda explained. “The competition of the two is going to improve the performance from the consumer perspective, which in the long run is great for advertisers.”