It’s hard to really provide insights in what rewards mining will offer you at this point.
It most likely depends on how much liquidity you provide in the pool & how much is provided in total, as rewards will be distributed evenly. There’s some good info under ‘liquidity mining’ here: https://uniswap.org/blog/uni/.
Myself, I’m looking to purchase more $UNI in the near future. Most likely around $2-2.5, I’m expecting this to hit shortly as many people immediately try to cash out their ‘airdrop’.
I can’t tell you which provides you better returns, can tell you that mining is most likely less risky as you’re not directly putting your capital at risk. You’d only be able to lose out on the swap rates (e.g. if you provide liquidity on USDT/ETH and ETH goes down in value).