Purport

To the question asked by Arjuna, for which of two types of devotees are better

1. Those who worship manifest God(The God in specific physical form) using manifest methods of worship. This is what called as Sakar Sadhna or idol worship by many

2 Those who worship un-manifest, invisible God using the non-manifest methods of worship. This is what called Nirakar Sadhna or non-idol based worship.

Shri Krishna gave a very clear answer. Shri Krishna explained though both types of devotees attain the same goal, but those who worship manifest God, that God which exists in some form is the best among all devotees. In other words, among all worship methods, the idol worships are the best. Why idol worship is better is answered in the next Shloka, but in this Shloka Bhagavan Shri Krishna made is absolutely clear that worshipping a manifest God, or worshipping one or other form of God is best.

The curiosity of the question ends here. What most can be done further in these three Shlokas to describe the words or phrases used.

In Shlokas #2 above Bhagvan Shri Krishna used the term like “steadfast in me”, “always worship me”. Those devotees worship Shri #Krishna in the form as he appeared during the Avatar. Shri Krishna as in #ShrimadBhagvadGita is a human entity, with a human form and shape, he was born in the house of Vasudeva and Devaki, spent his childhood in the house of Nanda and Yashoda, in war fields of Kurukshetra driving the chariot of Arjuna and in these Shlokas speaking to Arjuna. Those devotees who worship Shri Krishna who himself is the Supreme Lord hence worship a manifest God, A God with a specific form.

Such devotee worships one or other form of Shri Krishna. He does not or need not know about Shri Krishna, his potency, his power, or his nature beyond that human form which he acquires during the period of an avatar. He worships Shri Krishna by recreating the acts called Leela of Shri Krishna. The acts(Leela) of Shri Krishna are presented in the form of statues, images, stories, dramas, and plays and in bhajans. This whole worship method hence what called idol worship in a distorted form.

Bhagvan Shri Krishna in Shloka#2 very clearly specify such worship is best and such devotees are best among yogis.

But worshipping un-man fest God (nirakar sadhna) is not wrong. It gives the same destination as worshipping God through his forms. The difference, as described in the next Shloka such worship to un-manifest, is difficult to practice, hard to grasp and comprehend and has fewer chances to succeed. But if one can choose such a path and able to sustain it is equally good. Many Tapasvis, seers chose to practice meditation in isolated places for years. They don’t perform any worship, do not use any methods of worship but concentrate solely on the un-manifest form of God. Indeed they are able to achieve the same goal of reaching to Shri Krishna.

The conclusion: is both methods of worship give the same results, but Sakar Sadhna(Worship through forms fo god) is best.