Need input on choosing central air, and old vs. new refrigerant

I have received 2 quotes for a new central air system. The Lennox contractor offered 3 units - Merit 10 , Elite 11 with scroll compressor, and Elite 12 with scroll compressor and R410-A refrigerant. He thoroughly explained the new/old coolant issues and regulations. He did not at all push the Elite 12, even though it was the most expensive, and seemed to favor the Elite 11 as the best value.
The Bryant contractor offered a 10 SEER Freon unit, and an 11 Seer Puron (R410A) unit, and was strongly pushing for the Puron unit. He also explained the coolant issue thoroughly.
I am stuck between the Lennox Elite 11 at $2300, and the Bryant Puron at $2450. I was leaning toward the Elite 11 due to the scroll compressor, which they explained was quieter, and had less moving parts to break. But should I go an extra $150 and get the Bryant Puron unit? (the Lennox Elite 12 with R410 was pricier than Bryant's equivalent). I am not too concerned about the SEER. I think a 10 or 11 is fine for my area. The warranties are the same for each of these units. Would it be better to save the $150 right now, and take the chance that the unit will be fine for the next 10 years or so, or should I go with the Bryant Puron? The Lennox guy and the Bryant guy were like night and day on their opinions of the new/vs old coolants, as far as the importance of getting the new stuff.
Another question - how do I know if they did a cooling load study on my home? They both measured the house. One of them asked about insulation, and went up to the home's second level and took a quick look around. Both gave me a complete quote on the spot. From what I have read, the study sounds more complicated than that. Or are they able to judge by their experience in the area ( I live in an older tract subdivision, where lots of the homes are similar, both are local contractors). They both quoted 2 1/2 ton units, which coincidently is the sq footage of my house divided by 500.
Any help would be appreciated. Also any input on the quality of the brands, or is there a better one comparably priced?
Thanks for any help you can provide.
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A WAG in AZ is 400-450 sqft a ton depending on ceiling heights and glass. Higher ceilings and a some sun facing glass go lower. Your location will be different
Get a third quote for another brand of equipment.
Personally I would stick with r-22, freon the stuff everyone is using. I do not see it disappearing for the next 15-20 years. Being on the bleeding edge of technology is always risky.
Scrolls are quieter, and will probably last longer. I would also ask for the amp draw on the compressor, lower is always better. 10 Seer is the absolute minimum in today's market. I would be looking at a 12-14 minimum especially if I was staying for more than 7 years.
http://198.147.238.24/ac_calc/default.asp
Play around with this and see if it helps.
The installer is MORE IMPORTANT than the brand of equipment. Make sure your getting a new to-stat as well and filters. Might not hurt to clean the ducts before installation of the new unit
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Thank you for the help.

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