Of the Leopold and the Ducky, I'd go with Leopold since its cheaper, they are roughly the same in quality, especially with the PBT keycaps.
Now if you can get a used HHKB in fully working condition for roughly the same price (like less than $150), I'd definitely go for it if you have the time to spend cleaning it out. Won't get a good deal like that elsewhere. If its more in the $200+ range, it would really depend on your budget.