Rehab by a management company or a contractor?

[Wenlong Zhao]

About the rehab step, it is commonly advised to work with a contractor but get advises from our property manager on the scope of works. 
But many property management companies also offer rehab services. I'm wondering if it's better to find a contractor by myself or let the management company do it. Shouldn't the management company know better what repairs/upgrades have better return in the local market? 

Appreciate if anyone can share your thoughts on this.