Hadith: The garment that the Messenger of Allah (may Allah's peace and blessings be upon him) liked most was the Qamīs (long shirt)

عن أم سلمة رضي الله عنها قالت: كان أَحَبَّ الثِّيَابِ إلى رسولِ اللهِ صلى الله عليه وسلم القَمِيصُ.
[صحيح] - [رواه أبو داود والترمذي والنسائي في السنن الكبرى وأحمد]

Umm Salamah (may Allah be pleased with her) reported: The garment that the Messenger of Allah (may Allah's peace and blessings be upon him) liked most was the Qamīs (long shirt).
Sahih/Authentic. - [At-Tirmidhi]

Explanation

The garment that the Messenger of Allah (may Allah's peace and blessings be upon him) liked most was the Qamīs (long shirt) because it covers the body better than the Izār and Ridā'. Also, because it is one piece and thus easier to wear. However, if you are in a country where people are used to wearing Izār and Ridā' and you dress like them, there is no harm in that. The important thing is to not oppose the style of the people of the country, thereby becoming famous for it. Indeed, the Prophet (may Allah's peace and blessings be upon him) forbade wearing garment for fame and vanity.