First lets look a the movie promo Mewtwo

HP = 70
Weakness = Psy
Resistance = None
Retreat Cost = 2 Energy
Moves:

One Psy Energy Energy Absorption: Choose up to 2 Energy cards from your
discard pile and attach them to Mewtwo.

Two Psy Energy Psyburn   40
One Colorless

We all know this is a great card. Its great in mid game because of
Energy Absorption. Not Only that but you can discard the energy with a
comp search and get it right back. Great Card in the right deck. Now we
look a Team Rocket Mewtwo.

HP = 70
Weakness = Psy
Resistance = None
Retreat Cost = 2 Energy
Moves: Note: These moves are Translations of the Japanese pokemon.

One Psy Energy| Change Damage: Flip a coin. If Heads, Exchange all
damage counters on Mewtwo with those on the Defending Pokemon.

Two Psy Energy| Hypnotic Wave:  20
Flip a coin. If Heads, the Defending Pokemon is now Asleep.

Three Psy Energy|  Psycho Burn  60
One Colorless Energy|

Now This Mewtwo is basically the same as the promo but the moves are
very different. Change Damage Can be great but can be useless too. It
all deepense on the Defending Pokemon. He's next move Hypnotic Wave is
cool. You can now attack with only two Energy. With a chance of putting
them to sleep. His next move Psycho Burn is great for me because I find
that I keep my Promo Mewtwo on the bench for a long time, more than
enough to fully power him and even if he does not get fully powered he
can attack. But this is just how I play you should evaluate how you play
and decide which Mewtwo is right for your style of play.

bigdog2100
bigdog2100@home.com