There is no one ‘best’ cloud playout solution provider. They all have their strengths and weaknesses. I would recommend you to consider following criteria to find one that suits your needs the best.
Which cloud are they using? Generally public cloud services such as AWS will offer higher security, and thus your content assets would be better protected.
How good is the playout management experience? You should be able to add asset, modify playlist, and monitor from a single interface. https://www.techtiq.co.uk/php-developer Otherwise it becomes complicated to keep track of all processes.
How competitive is the pricing.
Hope this helps!