Will Gold or Silver ETF be a better investment option in terms of long term returns?

Yes, dollar debasement activities by FED and inflationary preasure will favor Gold and Silver in the long run. If you are interested in Trading gold or silver, GLD and SLV are good vehicles as they are more liquid. But If you have conerns on counterparty risk, i would say buy physical Gold and silver.

To answer your second question, I use gold as a portfolio insuarance rather than a dividend play. In addition, current Macro conditions are in the favor of gold. You can think of it as a captial appreciating instrument with less volatility.​​​