Very simply, it is a better rendering of his name in English. "Jesus" is the Hebrew to Greek to English translation. "Joshua" is a Hebrew to English translation without paying heed to Hebrew pronunciations.
Secondarily, and sadly, the name "Jesus" or "Christ" or the phrase "Jesus Christ" has been so badly associated with false stuff by the people who make up the christian religious system that it has become little more than a curse word for the world, and a religious talisman for the religious people of the world.
In other words, if I say the phrase "Jesus Christ" in a non-curse context to the average person, they normally 'download' into their mind the false or wrong stuff that the religious people believe and have spread across the earth in that 'name'.
So, a person with a pentecostal sect will associate their 'Jesus' with all the stuff Paul teaches about 'holy spirit' manifestations.
Or a person with another of the thousands of divided sects will have their 'Jesus' who condemns all drinking of alcohol.
Or a person with yet another of the thousands of divided sects will have their 'Christ' who commands that women wear head coverings.
Or a person with yet another of the thousands of divided sects will have their 'Jesus Christ' who insists that they have their meeting on Saturday instead of Sunday.
Or a person with yet another of the thousands of divided sects will have their 'Jesus' who is mad if a person eats pork.
Get the picture?
Just to be clear, the real person Joshua of Nazareth doesn't care about any of those things people divide over!
"Jesus Christ" has become synonymous with a book, the bible, with it's many hundreds of contradictions and wrong teachings about God.
The one thing the world get's right about the religious people's "Jesus Christ" - due to the hypocrisy of the people who somehow associate with that name by taking some christian label or by going to their buildings they call 'the church' - is that he isn't worth listening to.
So, if I am talking to someone about my Master, why bring in all that confusion associated with "Jesus" or "Jesus Christ" or "Christ"?
Perhaps what is most important about this small issue is what we do with the PERSON behind what name we give him. It really doesn't matter so much what we call him...what matters a lot is what we do with his person...do we listen to him and learn from him and do what he says? Or are we like religious people who 'Praise his name, hallelujah !' all the while not listening to HIM nor doing what HE says?
Please, enter into his Life and come, join the peaceful revolution!