RedDog, yes I have been around a couple of them and said many times that the CK and the DK line impresses me. Further, I seriously considered buying a DK40/45 (the Cub version), and if they come out with an HST version I probably will, if they don't then I'll probably upgrade my Kubota to another one or perhaps to a NH.
What is being missed here is the BIG picture. Focusing only on weight when a primary purpose of this tractor is to run a PTO powered implement that the CK20 barely has enough power to run is a critical issue. As this guy is obviously a landscaper doing jobs commercially, it is more important to focus on TIME = MONEY rather than weight = traction. As the Rota Darian guys told him he could use the Kioti but he'd have to go REALLY SLOW because of the low PTO hp, it simply makes sense to consider that as probably one of the biggest factors.
As for the weight issue, the
B7610 is a ladder frame design, by its very nature it is a light weight, yet strong structure. The weight is not in the engine housing, it is designed out of that housing and supported by the frame.
As to your real question about how I can say that the weight is not a real advantage, that is pretty easy to answer with practical use. Neither tractor is capable of efficiently & effectively operating a 5' box blade in a commercial operation where TIME = MONEY. Both are capable of operating a 4' box blade. As both are HEAVY ENOUGH to run only the 48" box blade, there is no REAL weight advantage. Since their practical limits are the same, from the standpoint of the capabilities with a box blade, they are equals. Go back and read all my comments, I pointed out where the CK20 was superior to the
B7610. I, however, focused on the issue of PTO hp as that seems to be the most critical issue the original poster has to deal with, and you'll also see where I recommended and he dismissed the LK series (didn't go slow enough). He also is very concerned about size so when people brought up the CK25/CK30 to get the critical PTO hp they also suggested a size he could not use. I went back to the
B7610 as being the same size as the CK20 but giving him the critical PTO hp.
This can be argued all day long. There are a lot of tractors that will generate the HP he needs, in the size he is looking for, with the HST transmission he needs. And as long as they can pull a 4' box blade effectively, they are heavy enough. I focused on the 2 brands he asked about.