I have read there are different intreprations of how the menorah is designed. There are the ones by Rambam that have straight arches going up and there are the circle arches by different rabbonim. Which is the correct way and what torah sources are there on this.
Illustrations from the time of the Second Temple, and from after that time, show the Menorah as having rounded branches. This illustration is even found on a coin from the end of the Second Temple era, and for this reason, historians agree that the Menorah had rounded branches. This is the basis for the model of the Menorah fashioned by the Temple Institute of Jerusalem.
This opinion is also stated by Ibn Ezra (Shemos 25:32). Even assuming the branches were rounded, there is some debate as to whether the branches were semicircular or elliptical. Other archeological evidence suggests that the branches were polygonal.
However, Rashi is often interpreted as saying that the branches were straight, and the Rambam, depicted the branches as being straight in two manuscript drawings. Some maintain that this means to be an accurate depiction.
Therefore, among halachic authorities, some draw the Menorah with straight branches, and most draw it with rounded branches.
Because the Torah does not specify the form of the branches (rounded or straight), both will be valid for the Temple.