Cryptopia of course! I previously trading on poloniex but have long since moved to cryptopia and all this time I have never had problems with deposite and withdrawal. Everything went smoothly and was fine. It's just a matter of volume, of course still far from poloniex but I still like to use cryptopia.
You are right Cryptopia is the best option when compared to Yobit because some times they are delaying everything by not sending withdrawals to its members. Even their support people are not up to the mark, they are not at all responding to the email we are sending.
Never heard any fatal problem on cryptopia and I would trust my cents here rather than yobit where that exchange are full of shitty errors around and also what I love the most on cryptopia is they've got a huge buy support on each coin listed there, I remember those early days on pesobit before where the price of it was bursted go up for more when it added there.