I would go with a Tegra3 based device, either a phone (non LTE HTC One X for example) or a tablet (Nexus 7 or Asus Transformer Prime for example).
Not many, but there are a few games that are optimized for the Tegra3's special effects. Like I said, not many, but when they do, its a whopper, like Shadowgun. The Tegra3 will run Android games just fine, but there is a growing number that has special routines designed to detect, and then make use of the Tegra3's special effects.
Other than that, phones with quad core CPUs or the 4th generation Qualcomm (eferred to as the Qualcomm S4), will also, like the Samsung Galaxy S3, will do quite well.
If you are looking for an Xperia phone, better wait till the next generation with the Qualcomm S4 chips comes out, though the current generation with the Qualcomm S3 does fine (but why pay for something that will be outmoded soon anyway). If you want to go cheap, look for the Xperia P or U, which has the Novathor chip, which has the same graphics unit as the Samsung Galaxy S2. Even these phones --- considered mid to low end --- will do much better on game performance than the Xperia Play. Do note these phones are not available in the US. With your best Xperia choice being the Ion, I would probably look for a Galaxy S3 or HTC One X instead.
Heck, for the price of the money, I would go for the Nexus 7 tablet instead. Can't beat a quad core Tegra3 tablet for $199.
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