I guess cos alot of films come out in twos - volcano/dante's peak; armageddon/deep impact
also of course there is there story line of revenge after a love one has been killed and somebody trying to figure out how a special trick is done.
So yes they are different films of course but it's not that much of a stretch why they are being compared - especially as in the USA they came out quite close to each other(albeit in a different order I understand)
For me the Prestige wins hanRAB down - hopefully seeing it again tonight (3rd time) and will buy the DVD for sure.
The Illusionist is a love story with zero chemistry between the two leaRAB which is odd because the guys who played the characters when they were young seemed to have bucket loaRAB