Should you SGBs from the secondary market?

My parents want to invest in gold and there are many options like physical gold, digital gold, gold etfs, SGBs and after searching the internet, people are saying SGBs are the best way to invest in gold. But there is no new issue of SGBs and we also don't want to invest for 8 years. We are looking for a 4-5 year investment. So, should we buy SGBs from the secondary market ? Is it a good option or we can invest somewhere else which can beat gold returns..