Thanks @ChaitanyaC for posting the Finshots article, I was about to post the same when I read few days back but got some other work 
So IMO, the reason why its trading at double premium is :
Muthoot is trading double the premium of Manappuram is because Muthoot is rather taking a conservative approach and consistently delivering it. Whereas Manappuram is aggressive and their plans are often disrupted by the external factors like in 2013 and 2020 covid crisis as mentioned in the above article especially refer the Manappuram profits hugely came because of auction. But they constantly agile and trying to stay competitive is really good.
Obviously both are good companies for long term. But for myself, I can be aggressive on any other sector but particularly when it comes to Banking and NBFC space I am slightly conservative. So When NBFC sector already have an issue of loans being not repaid, conservative investors happy to pay double premium to Muthoot.
So Manappuram fanboys don’t come and post 100 articles and PPTs to bash me saying that its the best. I am not saying or talking about which is best or worst.
Muthoot (for conservative investors) , Manappuram is for aggressive Investors. Period.
For more about Gold loan Industry and their comparison, I found this blog is really helpful.
https://soic.in/blog-description/playersingoldindustry
Then coming to @Ashutosh_Sancheti question regarding Rupeek :
The document posted by @Vinay_T_M was really helpful.
Page No: 6 last question have the answer for you.
Finally for the above Business Standard article,
UBS tells to “get out” but in the last para of the article “Others are more optimistic and Goldman Sachs Increased the Target” 
But this newspaper guys wants to panic you with the negative title.
So “News” and “Noise” are 2 different things where an Investor need to understand which needs to ignored and which needs attention. – Said by “Who knows” 
So for long term investors of Muthoot or Manappuram, we can classify as “Noise”
Just read this how much gold delivered since Independence. Though I prefer Equity over Gold, I have 5-10% for hedging purpose.