Storefront glass replacement is one of those jobs where the decisions that matter get made before anybody quotes it. Here is what to settle first.
Glass only, or the whole system?
If the aluminum is straight, properly anchored and not corroded, the frame stays and only the glass changes. That is faster, cheaper and far less disruptive. Replacing the system is for framing that is bent, framing whose anchoring has failed, framing so obsolete that stops and gaskets are unobtainable, or a change to a glass make-up the existing frame physically cannot hold.
Ask any contractor which of those applies to your building, and ask them to point at it.
What make-up you actually need
Tempered is the sensible default for most storefront glazing. Laminated earns its extra cost where there is a security history, a fall-through risk, or a noise problem. Insulating units matter where the space behind the glass is conditioned and the energy bill is somebody’s problem.
You do not have to choose one for the whole elevation. Laminated on the vulnerable ground-floor bays and tempered elsewhere is common, looks identical, and only pays the premium where it does something.
Matching
Replacement glass has to match on thickness, tint and coating, or the new panel will read differently from the ones either side of it — obviously so on a flat elevation in daylight. On older buildings the original glass is sometimes no longer made. A good contractor tells you that before ordering and usually recommends doing a full bay so the difference looks intentional.
Disruption
Most storefront work in occupied retail happens evenings, overnight or at weekends so the business trades normally. Establish that up front. If an opening cannot be closed up the same night, the contractor should be securing it before they leave, and you should hear that as a plan rather than an improvisation.
Comparing quotes fairly
Three questions make two quotes comparable. What frame depth is priced, and is it thermally broken? What is the exact glass make-up, including coating? And what is the lead time on the glass, separately from the aluminum?
A glazing specialist can walk you through all three. The answers also tend to explain why two numbers that looked similar are not describing the same job.
What to have ready
Rough opening dimensions if you have them, photographs of the frontage and of the frame profile, any history of breakage, and your constraints on trading hours and access. That is enough for a contractor to come back with a real scope instead of a placeholder number.