My wife and I looked at both Fuzion and Voltage. Work with a guy who pulls a 40' Fuzion and has had no major issues, just minor warrenty work. IMO they both are very similar as far as quality goes, they both are on the same priceline. Since Thor industries own both Keystone and Dutchman I don't think you are going to find a whole lot of difference in workmanship. I have read where people hated their Fuzion because of poor quality, I have equally found the same for the Voltages. I haven't done this but I am pretty sure you will find that on any trailer and RV. But how many times have you read someone starting a thread "My TH is awesome!!!!" the mojority of people will start a thread by stating their disapointment, not their satisfaction. The only time you really see someone stating there satisfaction is when someone is complaining about their RV and someone will chime in stating they are happy with their purchase.
All in all its going to come down to personal perference and you will be amazed that it will be something small to sway you to one model or another. Ours came down to the bedroom, we wanted the north/south bed, two access to main bathroom. Both voltages and Fuzion had everything we wanted, what really swayed us was that most of the Fuzion models have this offset North/South bed where it wasn't centered in the room. The Voltage is centered and has equal walk around room.
We opted for the 2014 Voltage 3950 and so far we are pleased.