Praise be to Allah.
To know the difference between these two types of hadith, it is essential first of all to explain what is meant by each term, and the different scenarios in which the scholars apply these two descriptions to reports, then to highlight the similarities and differences between them.
The scholars apply the description of munkar (odd) in the following scenarios:
The first scenario is some cases in which a report is narrated by only one narrator. That includes the following:
The hadith is narrated only by a narrator who is classed as sadooq (sincere), but is of lower standing than those who are precise in narration, and there is no other report (from other sources) to support it and raise it to the level of being saheeh (sound). We see this in the writings of Ahmad ibn Hanbal, Abu Daawood, an-Nasaa’i, al-‘Aqeeli, Ibn ‘Adiyy and others.
The hadith is narrated only by a narrator who is classed as mastoor (one whose character is not known), or who is described as having a poor memory or as being da‘eef (weak), and there is no corroborating evidence to strengthen his report. See al-Mooqizah, 42; Tadreeb ar-Raawi, 2/278; an-Nukat by Ibn Hajar, 2/647.
The second scenario is some cases in which the report differs from other reports:
When the report of the narrator whose character is not known (mastoor), or who is described as having a poor memory or as being da‘eef, differs from the reports of other narrators of higher standing. If this narrator narrates many reports that differ (from those of narrators of higher standing), then he deemed to be matrook (i.e., his reports are to be overlooked and rejected). The description of a hadith as munkar mostly applies to this scenario.
When the report of a narrator who is thiqah (trustworthy) differs from the report of someone who is more trustworthy than him, or he narrates a report that differs from many other reports (that outnumber his report).
See: Tadreeb ar-Raawi (2/277).
The third scenario is types of hadith that are weak for other reasons, such as when the narrator quotes the hadith and follows it with his own words, and people think that those words are the words of the Prophet (blessings and peace of Allah be upon him), which is known as mudraj; hadiths with interrupted (munqati‘) isnaads; and hadiths of which the narrator is unknown (majhool). This occurs in the writings of more than one of the earlier leading scholars, such as Yahya ibn Sa‘eed al-Qattaan, Ahmad ibn Hanbal, Abu Zar‘ah, Abu Haatim, Abu Dawood, an-Nasaa’i and others. They apply the term munkar to these types of hadith.
See: an-Nukat by Ibn Hajar, 2/675; Tahreer ‘Uloom al-Hadith by ‘Abdullah an-Judayyi‘, 2/1036.
The scholars apply the description of mudtarib (confused) in the following scenarios:
The first scenario is when a hadith is narrated in many versions, none of which is better in terms of the strength of its isnad than the others, so that it is not possible to say which is more sound. It is valid to describe a report as mudtarib if it is not possible to reconcile all different versions. If it is possible to reconcile them, then it cannot be called mudtarib.
The second scenario is when there is uncertainty on the part of a particular narrator with regard to the isnad (chain of narration) or matn (text) of the report. Hence it may be said that “so and so [a narrator] was confused concerning it, so sometimes he said one thing, and sometimes he said something else.”
See: Tadreeb ar-Raawi, 2/308; an-Nukat by Ibn Hajar, 2/773
From the above, the difference between the munkar hadith and the mudtarib hadith will be clear, on two counts:
The description of munkar is applied when a hadith is narrated by only one narrator, when it is not possible for him to have been the only one, such as when one whose character is not known (mastoor) or one who is weak (da‘eef), narrates a report that has no known corroborating reports that could support his narration. In other words, in order to describe a report as munkar, there is no stipulation that there should be many reports that differ from one another. With regard to the term mudtarib, it is only used for a report that is narrated in different versions, then these versions differ from one another to the point that they cannot be reconciled and it cannot be determined which is more sound.
There is another difference, which is when there is more than one isnad. In that case, we look to see if we can determine which is more sound, then the less sound report is deemed to be munkar, whereas we cannot describe a report as mudtarib unless the versions are at an equal level of soundness and it is not possible to determine which is more sound.
And Allah knows best.