they are faster and cheaper, but they are not kyc free, and a lot of people don't have access to CEXs for various reasons. so exchanges like eXch are their only option.
I would argue if those big centralized exchanges are always cheaper and faster.
There are many examples of people accounts getting frozen, coins confiscated, and they sometimes charge hefty withdrawal fees.
faster and cheaper here was in the context of exchanging to stablecoins and the higher liquidity they have, as that what the discussion was about.
For eXch you don't have to register anywhere, no need to use email, you are not sending any personal information, there is no login, so for me eXch is faster.
eXch is faster if you want BTC, ETH, or LTC. but for XMR, the liquidity is almost always low due to high demand, and the same goes for USDT, USDC, and DAI.
i guess this is why the discussion about USDT on Tron started.