Compare the Kubota 125 to the Case-IH 125 Maxxum. Same engine hp and both MFWD. Kubota has 356 cu in vs Case-IH 411 cu in. Kubota weighs 9447#. Case-IH 10890#. Where is the other 1500 lb difference? More frame, heavier lift arms, drawbar, tranny ect. I believe the Kubota also has cast rear wheels in an attempt to get the weight up to 9447#. Case-IH has steel.
Kubota lifts 5203# but can be optioned to 9447#. Case-IH lifts 9680# but can be optioned to 12,185#. I do have some 3 pt equipment that would not be lifted with 5203# of lift and probably marginally lifted at 9000 lbs. I have the 12,185 lb lift option.
I have an additional 600 lbs rear end weights, 1000 lbs of front end weights and 250# weight bracket. (I could add up to 2000 lbs of front end weight.)
Your figure of 110#/hp would be 13,750 lbs. My Case-IH 125 weighs 10,890#, 1850# of weights is 12,740#. I have the larger tires, rear axle and heavier lift which probably adds at least 260# for 13,000#. Loader brackets are heavy 1" thick steel and probably add another 700#. This puts me near the ideal. I pull a 1200 gallon, 90ft boom sprayer weighing at least 15,000# over 1200 acres 3-4 times a year. I need the weight and bigger tires. Going up bigger hills, I wish I had a few more ponies. (Could have bought the 140 hp version.:thumbsup

Put on the FEL and HD bucket and probably over 16,000 lbs. My FEL can lift 5350#, the Kubota loader lifts 3838#. Potentially my Case-IH can carry and lift over 33,000 lbs with tractor, 3pt and full weight on the FEL. (The number is staggering) Can the kubota with its lighter frame and rear end take the weight and heavy use? I see almost no larger Kubotas in my area used for routine farm use. Occassionally see them used as a large utility tractor.
I have many Case-IH dealers and few Kubota dealers in the area. The Case-IH also cost less than the Kubota. In less than 2 years of use and 1000 hours, I have had to replace an 0-ring on a hydraulic fitting under warranty. Dealer came to the farm at no charge.
Like anything, it depends on your use and need. My 2 main farming tractors are Case-IH maxuum 125 and Case-IH 245. JD 4520 for the light stuff and JD 2305 for mowing. Old IH 1086 for fill in tractor if the 125 is busy and on augers, batwing mower ect. IH 806 propane if I need to somewhat brutish force for a brief task (no cab and leaky manifold). Old Farmall 560 and M tractor but I never get that desperate.