Samsung is using a big event in Barcelona to introduce its latest pair of flagship phones, the Galaxy S9 and larger-screen S9+. The devices are similar in appearance to last year's S8 and S8+, but add a more powerful processor and an improved camera that packs a pair of fun features: AR Emoji and Super slo-mo. (This video shows the new camera and features in action.

Why it matters: Increasingly, Samsung and Apple are not only competing against each other, but also against the fact that people already have a pretty powerful smartphone in their pocket.

Here are some other key features:

• U.S. models will be powered by Qualcomm's new top-of-the-line Snapdragon 845 processor.
• The main rear camera has dual aperture for better low-light pictures, while the larger S9+ also packs a second rear camera for zooming in a bit.
• The built-in Bixby assistant gains a couple new capabilities, including the ability to translate text the camera sees.

The details: In the U.S., pre-orders for the Galaxy S9 and S9+ will start March 2, with the devices available March 16. Exact pricing will vary a bit at U.S. phone carriers. Samsung is also selling an unlocked S9 for $719 and the S9+ for $839. Additionally, a trade-in program offers up to $350 off the device, while carriers will have their own promotions to lure new and existing customers.