Although Standard Chartered said Ether could reach $4,000 in the next three months, should the US Securities and Exchange Commission (SEC) approve spot Ethereum exchange-traded funds (ETFs) in May, traders continue to prefer Bitcoin over Ether.

The ETH/BTC forward term structure, which is the ratio between prices for Ether futures and Bitcoin futures over different maturities, has been on a downward trajectory, as per Blofin data.

"The downward sloping structure is backward, which means that traders expect ETH to perform weaker than BTC as time goes by. This shows investors are relatively more bullish on BTC's performance," according to Blofin's volatility trader, Griffin Ardern.

Days after the SEC approved spot Bitcoin ETFs last month, the ETH/BTC ratio rose 17% to 0.059. Ether's outperformance predominantly came from hopes the US regulator would soon also give Ether's spot ETFs the go-ahead. However, the ETH/BTC ratio has since edged back to $0.053, CoinDesk reports.

Furthermore, futures traders may be concerned about the SEC's definition of Ether as a security or commodity. Indeed, the SEC's lawsuit last year against Binance and Coinbase for violating securities law did not refer to Ether, convincing markets the crypto will be defined as a commodity.

However, JP Morgan is uncertain as to whether the SEC will classify Ether as a commodity by May and believes there's just a 50% chance spot ETH ETFs will get the green light this year.

"There is a lot of uncertainty around the ETH spot ETF, mainly because its Proof-of-Stake could place it in a different asset classification from BTC. Greater uncertainty could also mean greater volatility," according to QCP Capital.

The SEC recently postponed decisions on Blackrock and Fidelity's spot ETH applications. The delays may continue, says Bloomberg analyst James Seyffart, with the next key date being 23 May.