There is also heated debate about when the gospels were written, the order in which they were written in, and if they were added to at a later date.
For example, the Gospel of John is usually dated to within 90-110 AD for authorship. That's not a wide range. Luke is usually dated to 80-90 AD but a few scholars argue a date as late as 110 AD. That's about as extreme as the disagreement gets among serious scholars discussing canonical writings.
There also aren't substantial scholarly disagreements about the gospels being added to or modified -- there are passages that are widely agreed upon as additions, which will be marked in basically any Bible from the last 5 decades or so. It's a common lay theory that there were major rewrites in the 4th century (Constantine), but I'm not aware of any serious scholars of textual criticism who believe it, because the manuscript evidence we have is actually strong in establishing tight authorship dates and clear indications as to what has and hasn't been edited.
The actual disputes are over subtleties, like Matthew 5:22 talking about being angry with a brother [without cause]. The phrase in brackets is in most manuscripts but missing from many of the oldest well-preserved manuscripts, and there is disagreement over whether it was added as a helpful clarification or accidentally skipped because it starts with the same letter as the next word (in textual criticism, skipping a word in this way is called "homoioarcton". This is a well-established field with its own technical vocabulary.)
My comments in other subthreads detail why I don't treat the gospels of Judas or Mary as significant -- based on their later authorship dates, clear non-Jewishness in style and substance, and even their lack of names of people and places pointing toward them being written by non-eyewitnesses.
The debates are regarding the underlying source documents that were used to assemble the gospels. E.g. Was there a Q? What was in Q? When was Q written? Who wrote Q? Why do the gospel stories have apparent contradictions? Who wrote those stories? Why? When? Based on what? How did they decide what to include and what to exclude? Do we even know what the original disciples thought of these stories?
There is so much we don't know about that first 100 years. At some point certain collected writings were deemed more authoritative, and there was a systematic purging of any disagreeable texts.
If you accept that parts of the gospel were written later in the first century based on stories that had been communicated verbally over long periods of time between different cities, cultures and languages... then the difference between the canon and the apocrypha becomes a little more blurry.
E.g. The Infancy Gospel of Thomas also date from the second century, and clearly shows wild stories were circulating verbally then being written down and accepted as canon by certain remote churches.
To paraphrase Ehrman & Fredriksen, you can argue that the stories in the gospels evolved and were selected largely to make certain theological points, or to counter the prevalent arguments against the religious movement.