SushiSwap is a fork of UniSwap, this is an undeniable fact, however, it is going out of the shadow of UniSwap and we can see this from their recent 2021 year outlook. Sushi is heading towards more cooperation with other defi products while Uni is trying improve speed by transferring to layer two solution.
More and more people go to SushiSwap and it is supported by community. We can see these data:
Liquidity and 24 h volume in Uniswap:
Then we take a look a SushiSwap:
We can see the liquidity of SushiSwap is more than half in UniSwap, the 24h volume is also a bit more than half in UniSwap.
Now let's take a look at their market capital in coinmarketcap:
$5,640,706,911 UniSwap
$1,306,630,052 SushiSwap
We can see SushiSwap is only 23% of UniSwap, but its liquidity and volume are more than 50% of UniSwap. This contradiction will be corrected by the market.