BIT,
I don't think you looked at my performance charts. In fact, I know you didn't, because the chart I provided is supplied by Agusta-Westland (see the brochure, which is provided on one of the links).
The EH-101's "maximum gross weight" is 14,600 lbs, upon which its component lives and inspection intervals are based. In addition, it can hover OGE only at 14,600 KG, thus that weight is the one Agusta uses for its own range charts. At higher weights, it's flight performance is reduced considerably.
Were both helicopters to use alternate weights, (perhaps rolling takeoffs?) the range for both would increase, of course.
The "maximum alternate gross weight" for the EH-101 is listed as 15,600 kg , do you know how that changes its maintenance regimin and component retirement times? I do not know. The US-101 site may take advantage of the new rotors and other items to be designed as part of the new program, which could explain the much higher weight than the EH-101.