First - thanks everyone for answering most of my questions in the thread:
My first contractor (estimator) specified a 90kBTU Carrier (58CVA090), based on my 2200sq.ft. home.
My second contractor (estimator) specified a 70kBTU Carrier (58CVA070), because the existing duct work above the furnace is a 14" cylindrical opening, and won't allow the full 16k cu.ft./min that the bigger 4-ton unit can produce. He said if the duct work were bigger (or if I spent a jillion dollars redoing the duct in the home), he "would" have specified 90kBTU, but not in this case. Furthermore, he said the bigger unit would initially come on full blast at 16k cu.ft/min. and then cycle back to about 11k cu.ft/min once the furance detects the backpressure. So he felt the bigger unit would be a waste for me to get.
Question1: From what I've read on this board, it's better to get the smaller one in this case (70kBTU) because it will run steady, and more efficiently, than the larger unit, under the above circumstances. It is likely to cycle on/off/on less.
Question2: The kicker: Both contractors estimated the same $price within about 50$. I would have figured the smaller unit would be less, but my guess on this is that the profit from the unit is not much, and the real work involves installation costs. My gut feel from meeting both contractors is go with #2, especially his knowledge and attention to detail.