Higher-end cutters that are able to cut larger diameter stuff begs the question: Do you really want to be around all the racket that cutting huge stuff makes? My BH26, which was amply "tested" by the previous and original owner (commercially- mowed LOTS of rocks with it!), has managed to take all the abuse that I care to toss its way: I tend to find the limits on everything- with the RC I can only go so far as my nerves will start to fray before the RC frays!). In my experience it's tail wheels that are the weakest parts: when you're backing into brush with unknown stuff in there you can really put a lot of stress on tail wheels. I'd also want a cutter that is going to break before it breaks my tractor! (shear pins and slip clutches aside)
Decks rusting and such is likely a bigger issue for many (rust isn't real agressive here in the PNW), in which case thicker decks are a plus.