Lives: The similarities in their lives simply cannot be missed. Swami Prabhavananda was born in 1893, while Swami Nikhilananda was born in 1895. Swami Prabhavananda was an initiated disciple of Swami Brahmananda, the spiritual son of Ramakrishna while Swami Nikhilananda was a initiated disciple of Sarada Devi, the spiritual wife of Ramakrishna. (It is interesting that both have the same Ramakrishna-number -- similar to Erdos number in Mathematics -- 2.) Both of the Swami's were sent at a very young age to USA to continue the work started by Swami Vivekananda.
Both of the Swamis established their Vedanta centres (as Ramakrishna Maths outside India are called) in the west at Los Angeles by Swami Prabhavananda and in the east at New York by Swami Nikhilananda. They both became famous in the modern world for their books and lectures mainly centering around Vedanta. Swami Nikhilananda was well known for his translations of Shankara's works while Swami Prabhavananda was well known for his collaborations and interactions with people like Aldous Huxley, Frederick Manchester and Christopher Isherwood (the latter two are his collaborators). They both continued to be the presidents of the centres they started till the day they left this world. Swami Nikhilananda left this world at 1973, while Swami Prabhavananda left this world in 1976.
Works: I think that Prabhavananda gives a simple from the heart commentary, while Nikhilananda gives a more scholarly translation (I wanted to, but did not use the phrase more-accurate for Swami Nikhilananda).
- Upanishads: Upanishads: Breath of the eternal by Swami Prabhavananda was simple, refreshing and introductory. Swami Nikhilananda wrote two translations of the Upanishads. One of them a 4-volume edition (amazon-link) is considered a master piece in itself and also has the commentary on the Upanishads by Adi Shankara. It also has a near 100 page introduction. So that lesser souls like us can read the Upanishads, The Swami has also written one volume abridged edition. Even the latter has a detailed introduction (mostly taken from the introduction to the former). Both of these introductions are a great introduction of the Vedanta to any serious student. A major portion of the introduction -- in both the 4 volume and 1 volume editions -- is aptly titled "Discussion of Brahman in the Upanishads".
- Bhagavad-Gita: The Song of the Lord Bhagavad Gita by Swami Prabhavananda was very simple and beautiful. The translation by Swami Nikhilananda included a translation of the commentary by the Great Adi Shankara. It also includes a great introduction.
- Biographies of their Parama Acharya: Swami Nikhilananda is well known for his translation for the excellent translation of Gospel of Sri Ramakrishna (which I have not read) and its abridged version (which I have read). Swami Prabhavananda's disciple Christopher Isherwood has written Ramakrishna and his Disciples which is enchanting. I put it in the category of Swami Prabhavananda because of he is a disciple of Swami Prabhavananda. In the introduction of the book, he begins with the striking words: "this book is about Ramakrishna, the phenomenon".
- Other Works by Swami Nikhilananda: Swami Nikhilananda has translated Mandukya Upanishad including Gaudapada Karika (book not available online in USA. Only in RK mission book shops in India.), Drg-Drsya-Viveka and Adi Shankara's Self-Knowledge (Atma-Bodha). The latter book is commendable for its introduction that has a good introduction to Vedanta Philosophy, and its appendix that has a beautiful translation of many devotional hymns written by Adi Shankara.
- Other works by Swami Prabhavananda: The Swami has translated Adi Shankara's Viveka Chudamani Crest Jewel of Discrimination as well as Patanjali's Yoga Sutras: How to Know God. Swami Prabhavananda's Sermon on the Mount according to Vedanta is a book I would recommend to any Christian for the simplicity with which the core of Christianity (the Lord's prayer) echoes Vedanta.
May you read the works of the great men and progress towards realizing Brahman within Your Self.
[This post is another in admiration of Ramakrishna Math in spreading Vedanta in the west. Previous one is here.
About spreading of Vedanta in India, there is a third monumental figure, Swami Ranganathanananda. Describing him would be attempted in another post. Until then, read these wiki-entry, quotations from Ranganathananda, his obituary (he passed away in 2005) review of his biography.]