Illusionist and Prestige are both based on common theme of "Magic". The Magical era of 19th century is common in both movies, and coincidently both of them were released nearly at same time. Climax for both movies end up in revealing some suspense.
In spite of all these similarities both movies are contrastingly different in presentation, approach and plot.

Illusionist has Edward Norton and Jessica Biel in lead, where as Prestige has huge star cast like Hugh Jackman, Christian Bale, Scarlett Johanson and Micheal Caine and off course a high profile director Christopher Nolan. Illusionist presents a different treatment of magic in form of a art and surprisingly disguised, as none of the tricks are revealed; whereas Prestige brings about scientific methodologies and craft behind the magic. Now the biggest attraction about Illusionist is Edward Norton, whose acting is perfect and flawless, Jessica Beil has also acted well, infact every one has played their part marvelously. Hugh Jackman's acting in prestige is disappointing, where as Christian Bale has acted very well. Bale has impressed me previously in Batman begins, here he has proved himself as much better actor than anyone else in movie. Scarlett has smaller role, not to mention her acting, but she was looking gorgeous(*drool) through out.

I liked set-up and backdrop of Illusionist very much, typical 19th century mannerism and old buildings and monuments and architecture, its just lovely. The screenplay of Prestige is whereas more impressive, and direction is also good. Illusionist is more focussed on love and feelings and emotions compared to prestige which has more of professional rivalry and talks more about tricks and sciences and other such things. Both movies tries to present that trick behind magic has to be disguised and that's what makes it interesting. Prestige tries to build up suspense till end and finally it is revealed in climax. Illusion has also very interesting climax, which few will like very much, while other will react as if it was just okay.
One more interesting part of Prestige is Tesla, one of the character who is a scientist building an electromagnetic machine. I will reveal any details about the machine, but it is an interesting part of story.
Overall both movies are good, but I liked Illusionist much better than Prestige.Illusionist keep you in fantasy land and it always shows magic like real magic, not to mention Edward Norton. His character Eishenheim carries an aura of magician or rather an illusionist, and Norton makes it look flawless. I must say that illusionist is a must watch movie.