How is Sovereign gold bond versus Gold ETF?

Technically both are the same. Both invest in gold and have an advantage over inflation as gold prices.

The key benefit of Sovereign gold bond over an ETF is that the investor gets 2.5% PA interest on base price, whereas, in an ETF, you don’t get such benefit.

The key benefit of Gold ETF is they can be traded any time so they are considered more liquid funds, however, to trade SGB, you must have a buyer. SGB is traded in exchange but volume is very low compared to Gold ETFs.