Celebi and Jirachi's stats are the same and are very evenly distributed! So, I judge which is better by their attacks. Celebi's(grass / phychic) attacks .....very few are attacks with damage... ONLY ancient power and confusion. Confusion matches its type, but is a relatively weak phychic attack. Ancient power is a rock type attack, doesn't suit its attribute, and it's not that strong itself...and only 5 PPs -_-. Jirachi (phychic/steel) has many moves that suit its type!!! Phychic is quite a strong phychic attack. Meteor mash and doom desire are very strong steel type moves!!! it has many other aggressive attacks besides those, these two are just 3 of the strongest attacks of jirachi!
Let's see...Celebi has 7 weaknesses, one of which is a 4X one and Jirachi has two weaknesses, Fire and Ground.
Plus, Meteor Mash, Doom Desire and Psychic all get STAB where as Celebi gats one, Confusion, which has a whopping 50power! Guess which one gets my vote >.>;
I went for Celebi because she just rocks! Come on people! She can time travel! (and I know that Celebi doesn't have a gender, its just that if she did I think she'd be a girl. And calling Celebi a she/her has bacome a habit)
I have both, and I both like em', it's a shame that Celebi has so many weaknesses, anyways, I think Jirachi looks cooler, and it's types are way better than grass/psychic.
A - They are both dual Psychic types and Psychic is my second favourite type.
B - Both are useful in battle. Celebi is generally seen as a cleric/healer whereas Jirachi is more of the attacker cause of the many resistances.