Software proposals are hard to compare because the important differences are not in the price. These are the questions that expose them.
Who owns what you paid for
Ask explicitly: on final payment, do you own the source code, the designs, the content and the accounts? Get it in writing. Some arrangements leave you licensing your own website, which only becomes apparent when you want to move.
Related: ask where the code lives. A repository in your organisation's account, with your developers invited to it, is very different from one you have never seen.
What happens when they disappear
Not a hostile question — people change jobs and companies wind down. Ask what a handover looks like: is the setup documented, can another developer run it locally from the README, are the environment variables recorded somewhere other than one person's laptop?
A team that can answer this has built something maintainable. A team that cannot has built something only they can operate.
How you will hear about problems
Every project hits something. What matters is whether you find out in week two or at the deadline. Ask how progress is reported, how often, and what happens when an estimate turns out to be wrong. A partner who tells you early that something is harder than expected is worth more than one who reports green until the day it slips.
What testing means to them
"We test it" covers everything from clicking through once to an automated suite that runs on every change. Ask what breaks the build, whether there are tests, and how a regression is caught. You are not buying test coverage for its own sake — you are buying the ability to change the software later without fear.
Whether they will say no
A partner who agrees to every request either has not understood it or intends to bill for the consequences. Being told that a feature is a bad idea, and why, is a good sign.
How we approach it
You own the code and the designs. The work runs in a repository you can see, the setup is documented, and if a date is at risk we say so when we find out rather than when it arrives.
Tell us what you are trying to build. Related reading: ERP for construction companies.