The syllabus of CAT and XAT are very similar in terms of Quant and Verbal.
XAT quant has some questions from trignometry too, which doesn’t appear in CAT usually. The verbal section is more or less similar. However, XAT focuses on Critical reasoning in the verbal section too. This would include interpreting the point of views of different people by reading a paragraph.
Apart from this, XAT has GK and Essay sections, which is unique.
GK section can be managed well if you are well-versed with current affairs and essay is a general topic.
Also, XAT introduced a new scheme of negative marking from 2016. This scheme had negative marking for incorrect responses and also for questions not attempted (>13 questions only), i.e. you could choose to not answer 13 questions. After this, you will start being marked in negative for every question you don’t attempt. This is unique in XAT.