Two quotes, two very different numbers
You've got two quotes sitting on the kitchen table, and one is a few thousand dollars less than the other. In a town like Nixa, where plenty of folks are watching the budget after a rough stretch of humid summers and ice-prone winters, that gap looks like an easy decision. Go with the lower number, save the difference, move on.
Before you sign anything, ask what each quote actually includes. A surprising number of cheaper AC installation bids in this area leave out the indoor coil, the part that sits in your furnace or air handler cabinet and actually does the cooling work inside the house. Without it, you've got a new outdoor condenser bolted to an old, mismatched coil, and that's not really a new system. It's half of one.
Why this matters more in southwest Missouri than it sounds like it should
Nixa summers run hot and sticky, with the kind of humidity that sits on you from June through August. That humidity is hard on AC systems generally, but it's especially hard on a mismatched coil and condenser pairing. The two parts are engineered to work together at specific pressures and refrigerant charges. Pair a new high-efficiency condenser with a coil that's ten or fifteen years old, and the system has to work harder to pull moisture and heat out of the air. Harder work means higher electric bills and a shorter lifespan for the new equipment you just paid for.
A lot of the housing stock around here, especially in the older parts of town and out toward Ozark and Clever, was built in the 80s and 90s with coils that have been through a couple of decades of Ozark summers and winters already. Metal fatigues, refrigerant lines corrode, and coils accumulate small leaks that don't show up until the system is under new strain.
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Where this stops being a homeowner decision
Once you're past reading the paperwork, the rest is genuinely a professional judgment call. Deciding whether a coil has enough life left to pair with new equipment isn't something you can eyeball. It takes someone checking refrigerant type compatibility, since older coils were often designed for R-22, which isn't what modern systems use. It also takes a look at the physical condition of the coil fins and the drain pan underneath, because a coil that looks fine from the furnace closet can be corroded on the back side where you can't see it.
This is the point where a second, more thorough quote earns its keep. If one contractor wants to inspect the existing coil before quoting anything, and another is willing to quote sight unseen over the phone, that difference in diligence usually says more about the eventual quality of the installation than the price does.
What a complete quote should look like
A full AC installation quote for a Nixa home should spell out the condenser model, the indoor coil model, whether the coil is new or existing, the line set condition, and whether a changeout of the furnace or air handler is needed to accommodate it. If a quote doesn't mention the coil by name, ask directly whether it's included and whether it's new.
The cheaper number might still turn out to be the right choice, especially if your existing coil is only a few years old and compatible with the new condenser. But that should be a decision you make with full information, not one you discover six months into next summer when the system can't keep up with an Ozark heat wave and your electric bill tells you something's wrong.