I was first introduced to using Poloniex by my brother while in search for an exchange with more elaborate margin trading options to choose from. Poloniex currently support 25 assets for trading on a margin and this is what keeps me on using the exchange. I also appreciate the trade fees they charge, 0.125% for an entry-level trader at tier 1 which can still be slashed by using TRX to pay fees. On it's marginal trading, I get to interact with cryptocurrencies that many exchanges don't support to trade on margin and the interest rate paid for on poloniex is lower when comparing to other exchanges I have been hooked onto before. I haven't actually tested out at all on it's futures trading but noticed it's high leverage even for low volatile assets. And it's spot trading has good liquidity to trade with
Apart from Trading, Poloniex support flexible staking of coins with no lockup periods. I got to stake my TRX but honestly didn't enjoy the rewards in relation to the percentage annual yield especially when comparing to staking privately on my wallet but with support for flexible staking that allows me trade and withdraw my coins anytime, I might be sticking with it longer. Another thing about poloniex I like is it's regular competitions and support for DeFi.
I don't really know much history about poloniex but got to find out that the exchange was once breached but has since then revamped its security apparatus even down to its users. It's fee structure for making withdrawals on Stablecoins isn't good down to the very least and I hope that improves. It is still my number one spot for trading margin and I recommend it directly based there for it's margin