I've DONE SimpleMining and i prefer SimpleMining
SimpleMining.net is cheapest (still it depends how many rigs you planning to have)
Then you can set your hashpower to nicehash pool or normal pool like ethermine or nanopool or others or for example miningrigrentals in which you can sell your hashpower for certain number of hours and certain price. Selling 14% more than "avg" price works many times in miningrigrentals.
Still, you should get also consider stability, features, design, user interface, support, community and others.
Better just try both and see which one suits You the most.