Everything I've heard indicates they're not the same. The powertrains (I
believe) are the same, but purportedly the Kia is a larger vehicle. They
are, however built on very similar chasses.
I haven't checked reliability ratings recently, but I haven't been overly
impressed with the XG's reliability. It hasn't been horrible, but I
believe it's Hyundai's worst model in terms of quality. If the Acura
scores high marks in quality, that may be reason enough to go with the
Acura, or at least do some sort of statistical comparison between the XG,
Amanti, and Acura.