SummaryAs good as prequel, but... different
The GoodWell. Saying that it's the "exact same game" is not quite right in my opinion. XCOM: TFTD takes a bit different approach, and is much better at it, in many ways.
The game is deeper, darker, more terrifying. And the aliens! While Gill Men and Deep ones feel a bit silly, Tentaculats and other nice creatures of this sequel leave UFO: Enemy Unknown far, far behind.
Everything is more serious and suspense, depths of the ocean are darker, screams of dying Aquatoids run chills down your back and teeth of Tasoth are sharper... After playing TFTD, blasting sectoids on cabbage fields feels a bit silly, and you will come back to TFTD to find that claustrophobic, haunting experience that prequel lacked. In other words, you're not chasing little green men anymore, now it's your aquanauts being chased, in the depths of the oceans...
While most of weapons feel the same, technology feels a bit more realistic and your aquanauts in top notch armor don't look more like what they were supposed to be and not like lost funny astronauts as was in the prequel.
Loads of new (and better!) graphics, darker colors and less repetitive terrains add alot too.
The BadAs almost all reviews say, missions are way too long and difficult. Especially second level of the alien colony - whoever designed this map - totally overdid it. Maps are quite crazy too, and it feels almost like designer intentionally designed the map so chasing down that last alien would be so difficult. This becomes quite frustrating.
Also, while music is good, and definitely adds more to the atmosphere, all that deep and dark burden wears player off quickly. I personally preferred cyberpunk and somewhat thrilling feel of the original to this... endless terror and agony that TFTD sounds like. Still, sounds are heavily improved and overall feel fits better to the theme.
Spending few hours (missions) underwater makes you miss the daylight. Sadly, there's almost none in this game. This gives somewhat worn out and repetitive feel, especially since game is much longer and harder.
The Bottom LineIf you liked UFO: Enemy Unknown and seriously need more, pick up this game. But remember that techno-thriller'ish joyride of the first game is now replaced with fear-inducing, dark battle for survival.
And your chances for survival are low, much lower than before. Quite literally, if you're not a patient, experienced hardcore player, you WILL die alone in darkest depths and no one will ever know what happened to you. No merry civilians wandering around this time.