I think the big difference is that much of the research has been done on beet juice - so defacto that's what many people end up using.

Some people may also dislike the taste of beets and try to disguise it by mixing it with other juices.

However, I subscribe to whole beets and recommend against juicing. Why not get the fiber and all the good stuff as well as the juice. I grate them in my salads, put them in my burgers and meatloaf and I've been thinking of adding them to my smoothies - like in this great inspirational smoothie article:

https://www.sunchlorellausa.com/blog/jazz-your-healthy-smoothies-these-11-unu...

Oh yes, I also pickle them with live cultures. Delicious - esp. in the winter!