For 2 acres I would go with the smaller deck. You will get a better cut with less chance of scalping with the 54". I have one acre with a 48" deck that I wish was 46" or even 42" for a better cut. Go 54".
I've really enjoyed reading the various discussions comparing Husqvarna and John Deere while searching for my new lawn tractor. My new 2017 Husqvarna GT48DXLS was delivered this past Thursday by Boiling Springs Small Engines. My prior mower was the 2013 Husqvarna YT42XLS with 23HP Kawasaki and...