We could be months away from seeing two of the world's next smartphone flagships, if rumors hold nothing but truth. We've seen Apple's iPhone 6 and 6 Plus take over the market by storm, selling four million preorders in their first 24 hours of availability. Samsung, on the other hand, appeared to lag behind -- and everybody's expecting "Project Zero" as the downright resurrection to the gloom brought by the Galaxy S5.

If the cards we hold are all right, the iPhone 6S and Galaxy S6 are sure-fire contenders of the 2015 smartphone bonanza. It would be interesting to see how Apple tailors an -s version for its current iPhone 6. In Samsung's case, it would be interesting to know how the company manages to revive its S-line, most specially since we've been hearing rumors of an S6 Edge variant on top of other speculations.

We've curated all the hottest whispers surrounding our rival devices to date, and without further ado, here they are.

Release Date

If current reports are to be believed, the iPhone 6S and Galaxy S6 may actually be unveiled just around the same season. International Business Times reported that the Cupertino giant might be eyeing a Spring 2015 release for the iPhone 6S. Spring, of course, begins in mid-March.

On the other hand, the Galaxy S6 has been strongly suggested to launch at the next Mobile World Congress (MWC) in Barcelona, Spain, The event is dated Mar. 2 - 5. Business Insider killed other allegations, claiming that the device comes out in January's Consumer Electronics Show (CES). Accordingly, the Korean tech giant will instead be showcasing appliances in next month's event.

Design & Display

Previously, MacRumors cited reports claiming that one of Apple's 2015 releases would include a 4-inch model. This translates to a possibility for the iPhone 6S, though it would be surprising to see a minimized version of the iPhone 6 come later.

We have earlier reported that the iPhone 6S is also rumored to pack sapphire display. Sapphire is regarded as one of the strongest minerals, falling next to diamonds in terms of hardness. Corning's Gorilla Glass 4 was another cited option.

The Samsung Galaxy S6 has been rumored to feature an all-metal body, as well as a foldable screen. The idea of the metal frame seems to come from the Galaxy Alpha, while the foldable screen draws inspiration from the Galaxy Note Edge. Because of so much craze over the latter, the Galaxy S6 is even speculated to have an "S6 Edge" variant, which could either be single or double-edged.

Photography

John Gruber hinted over The Talk Show (Daring Fireball) that Apple's next camera system would be close to DSLR-quality. As we have previously noted, he seemed to point at a future handset which could either be the iPhone 6S or 7, both of which are churning rumor mills at present.

Samsung appears to prep its next flagship with an upped megapixel count. The Galaxy S6 is said to feature either a 16 MP or 20 MP main camera, while its front snapper allegedly houses 5 MP. Rumors also say that Sony's IMX240 camera sensor will be included, as we have written earlier.

Processor

Apple and Samsung are joining hands for the iPhone 6S' processor, as Digital Trends puts it. According to the report, the rivals will be working on the A9 chip, powered by 14nm FinFET technology. As a result, the processor consumes 35 percent less energy and delivers 20 percent more power.

The Galaxy S6 has been reported to come in two types of different processors: one that is powered by Qualcomm's Snapdragon 810, and another running the octa-core Exynos 7420 chip.

Operating System

Trusted Reviews wrote that the iPhone 6S has been speculated to launch alongside iOS 9 in September. This follows the products' unveiling expected in June's Worldwide Developers Conference (WWDC).

On the other hand, the Galaxy S6 has been suggested to pack the latest Android 5.0 Lollipop, featuring the celebrated Material Design and user-sensitive notification system.

Apple has not confirmed any information about the iPhone 6S and iPhone 7 at present. The same applies for Samsung and Galaxy S6 / S6 Edge.

Which device would probably take over 2015? Sound off in the comments section below!

Check out this Samsung Galaxy S6 concept video from Jermaine Smit.