It's tricky, because there are two main factors:
1) 'literal' translation vs 'dynamic equivalence'/ idiomatic translation. That means you choose how far along a spectrum of exactly translating the words, vs translating the ideas into modern, understandable English. Study Bibles will tend to use more literal translations, then add footnotes explaining.
2) doctrinal bias. For example, the New World Translation is the Jehovah's Witnesses translation, 'translated' (they didn't actually use a team of people who knew the languages involved) to fit their own ideas. So it adds words, and chooses to translate the same Greek word differently when it refers to Jesus as opposed to the Father, so that they can point to it and say Jesus isn't God. Less obviously, this goes on in most translations, especially the less literal 'dynamic equivalence' translations. This isn't necessarily intentional: if you're translating an idea rather than a word, you'll choose words based on what you think the idea is. You also lose a lot of subtle nuance.
So, KJV is a more literal translation, but was definitely affected by the doctrine of the translators and the King, and is written in 17th century English. The NIV is very 'dynamic', and so very easy to understand, but it does come from an evangelical perspective, so you can expect ideas to be translated from that perspective. If it's on BibleGateway, you can expect it to fit an evangelical perspective. The Jerusalem Bible and the New American Bible are Catholic equivalents.
There are some more ecumenical translations, translated by teams from several denominations who wanted the most accurate translation possible without doctrinal bias, so we could use them together. The RSV (Revised Standard Version) and NRSV are ecumenical translations that tried to be fairly literal, while still being clear. They seem to be popular, and considered to use attractive language. The Good New Translation (Today's English Version) is a 'dynamic' translation that, again, was ecumenical: it's very easy to read, although it makes non-standard phrasing choices rather than parroting the phrases in the KJV, and that bothers a few people. It puts clarity ahead of pretty phrases, and doesn't use words like 'prodigal'. That can be a problem if someone else refers to 'the story of the prodigal son' or 'the ark of the Covenant', and you don't know those traditional names for them, but it isn't usually a big problem.
But really, almost all translations will have the same basic stuff in them, and it won't make a big difference to most things. So find one you like, and understand, and worry about translations when you're familiar enough with the text for it to matter
And, of course, if you just want the pretty phrases that get quoted everywhere, get the KJV.