It's the only other option at the moment, since you shouldn't go anywhere near Wasabi for obvious reasons.

In terms of being cheaper - it's variable, and difficult to compare exactly. The fees for Whirlpool are all flat, as opposed to based on amounts or number of coinjoins. You have to pay a fee to join the pool, which depends on which pool you are joining. So if I join the 0.01 BTC pool, then my Tx0 pays a 50,000 sat fee. But I pay that fee regardless of whether I enroll one UTXO or one hundred UTXOs. Then each input needs to pay for its first coinjoin. So if we take the 0.01 BTC pool transaction I linked to in the first post, you'll see two inputs paying more than 0.01 BTC - one paying 5,000 sats more, and one paying 15,000 sats more. But then once you are in the pool and coinjoined once, you get unlimited free coinjoins for as long as you are happy to leave your coins in the pool.

So in summary, if you coinjoin a small number of UTXOs a small number of times, your relative fees are high. But if you coinjoin lots of UTXOs lots of times, the relative fees are much smaller.