Guessing you live in the southern states? as the York furnace they propose is 80% I suppose if you wanted to save even more ( higher cost thou ) is to install a 92%> condensing furnace if you actually have cold weather.
Also the other two companies that are offering the Heat Pump, what will you use for heat when the Heat Pump fails and may be down for a few days?
What about when the machine goes into defrost, will you need any back up heat to help temper the discharge air temperature while in defrost, as your basically in A/C mode during that relatively short period. I suppose if you live in the south that may not be to important, as chances your defrost periods will not be that long? A question you can ask them...
BTW the Trane web-site says the XR16 can reach up to 17 SEER depending on indoor selection.
The Carrier web-site say the 25HCE4 can reach up to 14 SEER depending on indoor selection.
The York web-site says the YXT can reach up to 19 SEER depending on indoor selection. Comes with a lifetime compressor warranty to the registered original owner and has a two speed compressor.
Certainly ask for matched AHRI rated systems for the Trane and York as chances the Trane would have a good chance at any rebates your state or local utility company may offer. The York having the highest SEER of the lot, should easily qualify. Didn't those two Contractors mention possible rebates to you?