The EVO 3D, Photon, and Samsung Galaxy S II Epic Touch 4G (SGS2) are all great phones but Sprint is expected to be dropping the price of the Photon and EVO 3D to $99 as the SGS2 is announced.
See the
Phone Comparison for details but here is a quick summary.
The Epic Touch (SGS2) is SAMOLED which makes it brighter with less power. Each pixel has it's own Light Emitting Diodes. A black pixel needs almost no power because the LED's are off. The display is a big power drain so using less power to show dark colors is important. Also black is almost completely black giving very high contrast and making it easier to read in daylight.
The EVO 3D and Photon use Liquid Crystal Displays coving a series of backlights that are always on. The LCD is like the "gels" that are used in front of theater lights to block different colors. The white light is still just as bright and hot, the gels just reduce certain colors. That is why the "black" on an LCD can look dark gray and why a black LCD background saves no power. The backlights are just as bright.
An LCD phone is thicker because it needs a backlight to make the light and the LCD layer to block the light. So the total volume of the EVO 3D is 40% morel than the SGS2. The Photon is 50% bigger than the SGS2.
The backlight layer also adds weight contributing to the EVO 3D and Photon weighing about a third more than the SGS2.
The Epic Touch 4G is also expected to add
Near Field Communication and
USB Host (USB OTG).
These are all 4.3" with the Photon and EVO 3D having 960x540 displays. They are all fast dual core CPU's with 1024MB of RAM. The SGS2 internal memory is expected to be 16GB like the Photon. The EVO 3D is 4GB. All three have microSD cards, HDMI, and DLNA. The SGS2 and Photon have 8MP rear cameras. The EVO 3D is 5MP 3D.
And in the end, no specs can tell you what will feel best to you. Sprint will has three of the best phones of 2011.