Larger turkeys tend to be older turkeys, and older turkeys tend to have less fat. This could make them dryer. I usually buy turkeys in the 12-18 lb range, so I don't know whether one in the 20-25 lb range will be drier. I agree with Aschie30 that you might be better off with two smaller birds: less likely to dry out, shorter cooking time, easier to handle, etc.
Brining the turkey will help keep it moist and also make it less susceptible to being dry if you overcook it.
If you buy a fresh turkey, just be cognizant that this doesn't guarantee it will be juicier than a fresh bird. Here is what Cooks Illustrated has to say:
We always thought it would be a good idea to buy fresh turkeys wherever possible, assuming they would be better. If you can buy your turkey at a local farm, that might be true, but supermarket birds labeled as "fresh" can actually be tougher and drier than frozen ones.
Why? Turkeys may be labeled as "fresh" if they have been chilled to as low as 26 degrees. But at this temperature, tiny ice crystals can form in the meat. If the temperature fluctuates (during storage or transport, at the supermarket, or on the way to your home), these crystals can melt, combine with neighboring crystals, and then refreeze. These irregularly shaped ice crystals will start to poke the cell membranes in the meat, make holes and the cell tissues in the muscles will start to lose their internal contents. Then when they are cooked, those birds will be dry."
I would think that the Ho-Kas sold through retailers who know what they are doing would be fine.