The old Sears might just need a new ignition coil or some other minor repair, so you might want to have it looked at before dropping money on something new- at least have the problem diagnosed.
Yes, the parent company of Husqvarna is also the same company that makes all of the riders for Sears. But Husky does have a high end line that is only sold at Husky dealers. This is much in the same way that Cub Cadet is the higher end line of tractors that are built by parent company MTD.
In the under $2k range which is your basic lawn tractors, IMHO you can just pick and choose what color you want because from anyone who makes them in that price range they are all spec'ed nearly identically and all function in the same way. (Box section construction, economy line vertical shaft engine from Briggs or Kohler, all belt drive, and sealed aluminum hydrostatic transaxles) The only difference is that buying one from a reputable (key word) dealer will often save you a lot of headaches over buying one from a box store or department store should problems arise. But the truth is one isn't going to last any longer than the other because it's painted in impressive colors.
It's not until you get to the tractors priced $2k and up do you start to see any real comparable differences with the machines.
-Fordlords-