The 25HCC5 is a good middle of the road unit. Over the 25HBC3 you get better outdoor coil protection (louvered coil guard vs. wire frame), less sound (compressor sound blanket), and of course greater efficiency. Because it's a heat pump, you still get the high/low pressure switches to protect the compressor in the base grade unit (with Carrier at least).
While the 25HBC330 and FX4DNF031 is a fine system -- if you can, I would go with the 25HCC530 with FV4 air handler (assuming 2.5 tons is correct -- get a load calculation done). If you plan on living in your home for a while, this will give you quieter operation, better efficiency, and better comfort. You can and should use a thermostat that can adjust the variable speed blower to reduce humidity (Carrier's thermidistat model TP-PRH is one example -- Honeywell's VisionPRO IAQ also works well). While I can't see your ductwork, I do not understand contractor 2's comment about the variable speed blower being a problem. With a single speed outdoor unit, if anything, it would help with airflow as it can provide a constant CFM (airflow) across varying duct conditions whereas airflow starts to drop off considerably with standard motors as pressure increases (dirty filter, poorly designed ductwork, etc.).
Where in MD are you located? I may be able to recommend a company or two if you are pursuing further estimates.