Have you been to either place?
There was a very positive review of this product in Fighting Fit magazine by a guy called BJ Rule. He's pretty experienced in the kettlebells.
There have been attempts made at adjustable kettlebells in the past. These have been ordinary at best. They weren't much other than a handle with a number of plates and a couple of pins attaching it all together.
In complete contrast to what's gone before, the Wolverson Adjustable Kettlebell is absolutely brilliant. It has the same dimensions as a competition sports bell. The shell weighs 12kg and there are five plates (3 x 4kg and 2 x 8kg), which means you can have anywhere from a 12kg to 40kg bell in 4kg increments. On the Wolverson site it says the bells can be as light as 6.5kg but I couldn't figure this out - unless you only use half the shell...
Mind you, the same magazine argued that Practical Programming wasn't up to much and wouldn't assist you in getting stronger.