Why not take the lowest bid?
RISK!!!
You risk getting what you paid for... PROBLEMS!
You RISK:

Hiring someone with Inexperience in handling site or weather challenges.
Improper setting of forms can lead to water standing on your slab or too
much slope on the tread of a step or walk. Failure to prepare for
different weather conditions can cause an unsightly surface and worse;
surface failure.

Ugly concrete due to poor workmanship: Finishing, sealing, forming,
and jointing problems can be very unsightly and may in many instances
cause scaling of the surface within the first few years.

Defective Concrete. Your concrete may be compromised because of improper
placement procedures.

A claim against your homeowners insurance. If you hire a contractor without
proper insurance you could end up footing the bill for injuries or damages
caused from the contractor

A lien filed on your home from an unpaid material or service provider.
A hauling company or concrete material company when not paid can be left
no restitution but to file a Mechanic's Lien on your property if your
low-bid contractor "disappears" without paying.

Hiring a contractor who begins a job and draws out a 3 day project to 3
weeks or more and continues to make excuses as to why he can't come to
your job.

Hiring a contractor who refuses to make restitution for any of the
above problems.

Hiring a contractor who won't return phone calls when there is a problem.
All of the above stories have come to us by homeowners who have called
us after they had hired the wrong contractor. A contractor who is willing
to cheat the government out of sales taxes, payroll taxes, and income
taxes is also willing to cheat the customer.
OVERLAND CONCRETE CONSTRUCTION