Bittrex is my preferred exchange. I've yet to encounter any hiccup or downtime. Poloniex on the other had seems to have issues almost daily. They lock withdrawl/deposits for alt-coins frequently, beyond simple wallet cleaning requirements. I also had issues with Poloniex losing my withdraws. I had to harass their customer service half a dozen times for a resolution to which they still never responded. Customer service is complete garbage.
Bittrex is my preferred exchange. I've yet to encounter any hiccup or downtime. Poloniex on the other had seems to have issues almost daily. They lock withdrawl/deposits for alt-coins frequently, beyond simple wallet cleaning requirements. I also had issues with Poloniex losing my withdraws. I had to harass their customer service half a dozen times for a resolution to which they still never responded. Customer service is complete garbage.