The 1500 and 1600 series are made by Mitsubishi, the 2500 and 2600 series are made by TYM. Both build a strong tractor and as RNeumann said, they have the same Mahindra no DPF motor design. The lift capacity difference has to do with the weight of the tractor and the loader design. I know TYM builds their own loaders, not sure if Mitsubishi does or if its built by someone else.
Retail price also doesn't mean much since they often have significant price drops from the retail list price. If you're interested in two different models then get quotes on both from the dealer. There can also be a significant price difference between the cash price and the financing prices. You pay more up front for a low rate financing and sometimes can get better financing rates from a local bank or credit union. Your dealer should provide a written quote on each tractor with a cash price and usually two different financing options.