Having not seen the 1973 version, I would like to offer some objective opinions. Please forgive me if I did not get the song names right, but I have named them after reoccurring lyrics.
Starting with Jesus. His vocal range is far to small for some of the higher notes, such as the ones in "understand what power is" in which he is very, very flat, but his falsetto is quite good. Also, it is interesting to note that although he has only 4 facial expressions (angry, distraught/frightened, joyful and blank) he manages to convey the emotions of the character very effectively through the timing of said expressions.
Simon: is one of the most aggravating characters I have ever seen. He looks fresh out of an American soap opera, and although he has a good voice and expresses the emotions of the character, I can't help but find his facial expressions rather amusing ("Jesus I am on your side") Judas: my personal highlight of the film. Expertly acted and providing a cynical touch to balance out the terminal perkiness of Simon. He manages to portray both sides of the story, the devoted follower of Jesus, and the almost prophetic and panicked alter-ego.
Pilot: truly wonderful performance. Sensitively acted, he was amazing.
Caiaphas: Fantastic voice. I nearly jumped out of my skin on his first low note. Supported by a fantastic group of actors as the high priests.
Herod: Not as subtle as it could have been.
In general, this is an excellent movie, although it is often melodramatic. If you are to enjoy it to the full, accept that it is a musical and isn't going to be realistic. It makes Jesus real, and does so in a very entertaining way. Combining a well thought out plot with strained lyrics (did you see I waved?), this is one of the best modernized period pieces I've seen.