hello, why lending rate for BTC on poloniex 3x larger then on bitfinex?
Market dynamics. Mostly dependant upon available currency supply, Bitfinex might catch up on size since they survived their hack from recent year. And introduced that strange BU token stuff (which I would not dare to touch with a ten foot pole) but seemingly this attracts deposits, so more supply floating on site resulting into lower rates.
Go for Poloniex if you are supplying lends, my advice.
For your information Bitfinex are taking their tokens off the market because it has achieved its purpose and they are starting to repay their customers who had funds stolen because of the hack. Good job on them for not scamming the community.