Both phones are really equal in power, so it comes down to the Motorola vs. Samsung brand name, a thicker phone with a sliding keyboard vs. a thinner phone with a larger, higher resolution screen. IMO, the new Motorola phones, so far the Photon Q is the second after the Atrix HD, are very competitive and underrated.
One question I have is that you're in Verizon and the Photon Q is only in Sprint. If your profile is outdated and you're already in Sprint, you might also consider the EVO 4G LTE, which appears to have a dedicated camera button and the cameras in the last crop of HTCs seem as good as Samsung, or better. They are certainly fast as well. There probably isn't anything like the Photon Q in Verizon until the unannounced yet Droid 5 will come along.
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