Hi newbie here, I need to buy an outdoor unit for my 2100 sq ft home in Savannah Ga. I have it narrowed down to 2 Trane systems. The first is a Trane XR 15 3.5ton system with a 15 seer rating. The other is a Trane XB 14, 4ton system with a 15 seer rating. Both units are priced the same and I can't decide if I should go with the 3.5 ton XR15 or the 4 ton XB14 ? I have a variable speed hyperion indoor unit (air handler I think its called) installed already, and my home is Spray Foam insulated, no Fiberglass insulation (if that helps) I just want to know what will be the best "bang" for my buck, and what are the major differences, which unit can best handle Hot Georgia weather and which system will be cheaper to operate? etc. Thank-you in advance for helping me.