I am from south India and recently wanted to learn Bhansuri flute so I ordered one online .But later just like you i found out there are two types of bamboo flute.
There are two kinds of classical music in India
1. Hindustani music
2. Carnatic music
So Bhansuri is used in Hindustani classical music ( north Indian) which consist of 6 or a 7 flute
Whereas the Carnatic classical music ( south Indian ) uses the venu which consist of 8 holes but most of the time only 7 are used.
The main difference in number of holes hence the fingering is different and also the venu is said to be able to produce more types of notes than bhansuri while bhansuri is easier to play and learn for begginers.
You can choose either of them .It is better to have a teacher to play venu because there is some technique involved in playing music .
Both can play really good music so you can choose either but begginer should prefer the Bhansuri ( will have 7 holes + 1 blowing hole).
You should prefer buying a medium sized c or g scale flute , should be of good quality .
I am a begginer like you .
Punam flute in amazon.in is a good quality one( just a recommendation not a spam)
Note: In the above picture left one is a carnatic flute venu while right one is a bhansuri.Observe the holes