Why you need stablecoin conversion
With the popularity of the DEFI concept from the Middle of June, stablecoins also had an eruption and the total market cap attained over 14 billion USD.

There are many scenarios that need to use stablecoins, but each scenario basically only uses 1-2 kinds of stablecoins. In order to diversify risks, users usually participate in as many scenarios as possible, so they need to hold a variety of stablecoins. This creates a demand for stablecoin conversion and Curve comes out. Since you could easily find enough information on What is Curve and How to use it, I will save my words for another stablecoin conversion platform ViteX.
Unlike Curve, ViteX is not a smart contract built on Ethererum. ViteX is a build-in smart contract and a DEX on Vite blockchain and it's released in July 2019. After the latest Hardfork, there is no trading fee for stablecoin conversion. Initially, three stablecoin pairs for zero-fee conversion are available now, USDC/USDT, DAI/USDT, and BUSD/USDT. To encourage more users to participate in this, users who provide liquidity will be rewarded. Besides, Vite is a DAG-based blockchain with 0-fee for transactions. Users could benefit a lot if they choose the ViteX platform to convert their stablecoins.
Yet, ViteX is not a perfect solution for stablecoin conversion. Its shortboard is the cross-chain gateway, which is not so decentralized for now. Fortunately, Vite Labs are trying to replace it with a decentralized solution soon and the foundation will endorse for current solution.

Comparison: Curve vs ViteX
Assets Security
When staking stablecoins to Curve, assets are managed by the contract and it's fully decentralized; on the other hand, if the contract went wrong, nobody could help you to get assets back.
When depositing stablecoins to ViteX, assets are managed by ViteLabs' gateway; though it's not fully decentralized, it's secured by the Foundation.
Service fee

Liquidity Rewards
Both platforms reward tokens to liquidity providers, CRV and VX.
Staking VX could claim BTC, ETH and USDT every day from ViteX's dividend pool, which collects all the trading fees from the platform.