Actually not that difficult to answer. But it depends on individual
thoughts and followings. Its up to us whom we worship or follow.
The way I see it is: In the Ramayan, Lord Sri Ram explains the nine types of devotion or penance to Shabri:
नवधा भगति कहउं तोहि पाहीं। सावधान सुनु धरु मन माहीं॥
and the very first said:
प्रथम भगति संतन्ह कर संगा। दुसरि रति मम कथा प्रसंगा॥
The first step to devotion (Bhakti) is to keep company of the saints (Satsang). The second step is to enjoy listening to legends/discourses pertaining to the Lord
So yes I follow Sai Baba as he was a saint and also because I completely trust Lord Sri Ram's words.
And about worshiping him, as I said, its up to individual's beliefs. They feel happy/relaxed by worshiping Sai Baba, so be it.
And let me complete it:
गुरु पद पंकज सेवा तीसरि भगति अमान। चौथि भगति मम गुन गन करइ कपट तजि गान॥
Selfless service to the Guru's lotus feet without any pride is the third step. The fourth step is to earnestly sing praises of the Lord's virtues with a heart clear of guile, deceipt or hypocrisy.
Here... Many people also considered/accepted Sai Baba as their Guru and that's also one of the reason they worship him as their Guru. And Worshiping Guru is not wrong because we only chant: Guru Brahma... Guru Vishnu...
मंत्र जाप मम दृढ़ बिस्वासा। पंचम भजन सो बेद प्रकासा॥
Chanting My Name with steadfast faith is the fifth step as the Vedas reveal.
छठ दम सील बिरति बहु करमा। निरत निरंतर सज्जन धरमा॥
The sixth, is to practice self-control, good character, detachment from manifold activities and always follow the duties as good religious person.
सातवँ सम मोहि मय जग देखा। मोतें संत अधिक करि लेखा॥
The seventh step is to perceive the world as God Himself and regard the saints higher than the Lord.
आठवँ जथालाभ संतोषा। सपनेहुं नहिं देखइ परदोषा॥
The eighth, is a state (which one arrives at when one travels the first seven steps) where there is no desire left, but the gift of perfect peace and contentment with whatever one has. (In this state) one does not see fault in others, even in a dream.
नवम सरल सब सन छलहीना। मम भरोस हिय हरष न दीना॥
In this state, one has full faith in the Lord, and becomes (child-like) simple with no hypocrisy or deceit. The devotee has strong faith in the Lord with neither exaltation or depression in any life circumstance (but becomes equanimous).
नव महुं एकउ जिन्ह कें होई। नारि पुरूष सचराचर कोई॥
सोइ अतिसय प्रिय भामिनी मोरें। सकल प्रकार भगति दृढ़ तोरें॥
Sri Ram adds that Shabri’s Bhakti is perfectly complete. Yet if anyone were to have taken even one step towards devotion, out of all nine, he/she would be very dear to the Lord.
Now, my question is: Didn't Sai Baba had all these 9 qualities?