The main differences between high-interest savings ETFs and Guaranteed Investment Certificates (GICs) are liquidity and CDIC insurance. High-interest savings ETFs offer liquidity, meaning investors can buy and sell shares on the stock market, while GICs have a fixed term and may not be easily accessible before maturity. However, GICs are typically insured by the Canada Deposit Insurance Corporation (CDIC), protecting the principal investment up to certain limits, while high-interest savings ETFs are not.