Confused on what AC Unit to purchase and install?

Confused on what AC Unit to purchase and install?

I am replacing a 30 year old AC unit and I have had 4 estimates. 2 of the
4 people did not even take any measurements and the other two took a lot
of measurements. I am leaning towards the ones that took measurements, but
they are giving me two options. I live in Florida. Here are the two
options:
3.5 tons 13 seer Ameristar straight cool
3.5 tons 13 seer Goodman heat pump
What is the difference between the above two and is one brand better than
the other?
Does anyone know some important questions I could ask the installers to
see which one maybe more qualified or knowledgeable in installing the unit
I found paperwork on the house and it indicates that a 3.5 ton was
installed in 1984.
The two people that did not measure apparently were salesmen.
One from sears told me this:
OK great give me a call or send me an email when you ready. You currently
have a 2 Ton and I can see going to above 1/2 ton more or a max 1 Ton more
not 1 1/2 Tons more. I will install what you want, and our system and
service will be better than any company out there. When you contract with
Sears you don't get a lot of plastic and thin metals you get a good
quality system that will last.
I don't understand how Sears can tell me I have a 2 ton when I have a 3.5
ton. Something smells fishy here?