HUT is a reseller for Berea kits. The pens are identical and the parts are interchangeable. Only the packaging, label, instructions, and sometimes the price will be different.
If you need the instructions, buy the kit from HUT because their instructions are better (my opinion). Otherwise go for the lower price.
Both Berea and HUT recommend a 31/64" drill for the main body. Berea recommends a 33/64" for the cap tube, while HUT recommends a larger 17/32" The cap tube can be a tight fit in the smaller hole, and may even require sanding inside the hole if there is any fuzz from drilling. For that reason, HUT is recommending the larger drill for the cap to make it easier to glue in the tube. However, there is the increased risk of turning through the wood