The categories shown in his estimate is completely different, so it's hard to compare apple to apple, and understand why the big difference in cost.

You'll find out that you can only watch that much daytime TV and non of your friends have time to hang out.

If you look at your neighbor, NY, there are so many markets that aren't in NYC that you can invest in that are vastly different than the Big Apple.

Literally every day was like watching an impossible to script reality tv show.I'd often ride around with him through Detroit for the day and the stuff I would see, phone calls I'd listen to, etc. were just insane.If you want to be successful with it I believe you MUST be local, super hands on, and enjoy the chaos.

Keep in mind using a PM CAN be a team-sport, you can work together for a greater finished outcome, vs just handing off and watching tv. 

Is the code required concrete pad at the outdoor installation point.Is it a ground, roof or cantilever type outdoor installation.Is the equipment all the same brand and size for all of the bids, or is it Carrier vs Goodman, etc..X tons vs Y tons.Are they all including coolant gas in the bid (the new stuff is astronomical in price).Are they including new copper lines in the bids, or just the inside and outside components in some bids.What I'm getting at above is are the bids apples to apples....It the whole Air Conditioning system magic to you--like pulling a rabbit out of a hat, and you are a fish out of water about how it works and it's parts and terminology?

I think your question is a very important one, and it would help to compare apples to apples.

A few bad apples spoils the barell! 

For sure, don't call anyone that you might hear on the Radio, see on TV, etc...

I recommend that you start by speaking with agents at those two companies and see who can get give you the best quote “apples to apples.”Some of my more experienced colleagues like @J.