Minergate will not perform as well as cpuminer, because the graphical user interphase requires some cpu to render. Therefore, if you want to maximize performance, cpuminer is best, but for newbies, minergate is great! If you're really paranoid, you can monitor the ports it is communicating through. I personally think it is safe. You are right that the high fees and high minimum payout are also not the best, but people can essentially ddos a service with too many low payment requests. Scanning the installer with an online virus scanner is a good idea too if you are worried.

But honestly, it is probably perfectly good software. Ultimately most mining brings in dismal profit unles done seriously large scale, so it is better to just buy some, until you can get serious into mining. But some people want to mine just for fun and the experience of creating money from electricity, evenbif it is less than a penny.