You could watch This Is Elvis and see one of Costello's two other concerts, but if Monday is your only free night, and, like me, you are a big fan of both. it could be a difficult decision. Both promise to be excellent shows.
This Is Elvis had a brief run in the cinemas a few years ago. but like most rock and roll movies its audiences weren't large —a shame because the film presents an excellent chronicle of the King's life.
The majority of the footage is of Elvis, although there are a few scenes where actors are used to portray Presley.
The film is an amazing portrait of Elvis from his fresh, vibrant, electric performances in the 50s to his tragic demise in the 70s.
The footage from Elvis' early years is particularly astounding. There are extracts from the Ed Sullivan, Dorsey and Milton Berle TV shows, including the performances when Elvis could be filmed only from the waist up.
Contrary to what most people believe, Elvis recorded some of his finest material in the 70s, and we see him in the studio recording the superb "Always On My Mind" soon after he'd heard Priscilla was leaving him.
There's also devastating footage of some of Elvis' final concerts, including a moving version of "My Way" recorded just before his death. And a further highlight is the home movie footage discovered in a basement of Graceland months after he died.
There are amateurish shots of Elvis and Priscilla's wedding, Elvis at Graceland, with his family, and with the Memphis Mafia.
Elvis Presley is likely to be the most charismatic and talented performer rock and roll will ever produce and This Is Elvis is as fine a tribute as we could reasonably expect.
As for the other Elvis, along with his arrogant stance and obvious talent, Mr Costello attracted a lot of interest early in his career because of his choice of Christian name.
Elvis of the Presley variety never got around to expressing an opinion, but Costello admits to not being a fan of Presley.
"I know this is heresy, but I'm not really a fan of his in the same way I'm a fan of many other people," Costello told me last week.
"l like all of the really early stuff, the Sun Records material, the really wild things. It wasn't wild in the sense of abandoned, but wild because it was before he realised what was good about himself.
"But he was a natural. Those early records on Sun are like Hank Williams's records — they sound like they are from a different planet.
"It was different after that because even before he signed with RCA and went into the Army, he was self-conscious. Elvis became self-conscious really quickly and lost a lot of his attraction for me because of that."
"There was a difference between me and Elvis Presley — he took downers and I took uppers," Costello said.
"He took drugs that put him to sleep. I took ones that kept me up long enough to think I was right.
"I was self-conscious, but I was so convinced I. was right for a couple of years that it didn't matter. I had to go from somewhere to somewhere else so I might as well go through being completely arrogant and hopefully come out the other side of it."
In Elvis Costello we have a performer who has developed the perfect hybrid rock and roll sound and executed it magnificently over the course of more than half a dozen essential albums.
Elvis is at the Opera House on Monday night and on May 29. On May 30 he's at the Lyric Theatre in the Entertainment Centre. Tickets are $19 and the Electric Pandas are the support.