Looks like the 55hp NH boomers are now using Fiat for the engines. Is there something about the new engines that is making you move away from NH? I'm only curious because I'm getting ready to trade in a 2008 Case Farmall 45 cab tractor for a Case 55C with cab. Like you my current one has 1,600 trouble free hours with the Shibura engine. It has never been in the shop.
The New Holland dealer I bought from is primarily an ag tractor dealer. Their shop mechanics didn't seem to be very experienced dealing with the smaller utility tractors. A recall repair was botched and required three trips back and I still had to fix some minor things myself. That plus New Holland no longer sources this line of tractors from Shibaura are the main reasons I not considering New Holland. I really don't know anything about the larger Boomer tractors or the engines. The Fiat engines were not an issue in my decision. Vic