Cannot find Anyone To Do Heat Loss - Two widely different Mini-split Proposals

I live in lower NY state, home out in open without trees/shade. I have a great room I would like to update the HVAC. The room is 35' x 21' with 12' high walls and ceiling peak around 24' high. New roof but medium dark triple ply asphalt shingle built in 1950 on a slab with 4" walls and whatever was standard insulation at that time. The two long walls (35' each) face East and West and these have about 50% surface with modern low-E windows or glass doors (12' slider plus transom on one of the walls). There is a large (5' wide) fireplace floor to ceiling. Currently no AC and the only heat source is a 60 year copper pipe hydronic (oil fired boiler) radiant ceramic tile floor (I think there is a 6" subfloor between slab and tiles). Given the age of the copper pipes and water quality in my area, I think the radiant floor will fail in the not so distant future. I would like an AC solution plus a hyper-heat system down to -5F or -10F.



The local Fijitsu dealer came out and said I needed two x 2 ton AOU24RLXFZH eXtra Low Temp Heat Pumps with 2 x one ton wall units at about 10' height on a long wall for one of the pumps and then 2 x one ton floor units on either side of the fireplace. 4 tons with no heat loss calculation based on his experience.



The local Mitsubishi dealer came out, and said one 2 ton top line MZ MXZ-C H2i (MXZ-5C42NAHZ) with a single wall unit place about 20' high on the short wall opposite the fireplace. 2 Tons with no heat loss calculation based on his experience.



Who do I believe ???? More BTU, more units always sounds better.



PLEASE any sound advice appreciated.



Jerry