Imo it really depends on what you want to do. Drafts are great to ride, and I know a wonderful registered shires that are great to ride and drive, and others that are not as agile. It depends not just on the breed, but also on the personal horse. For more athleticism, a draft cross may be better, as they tend to combine the lovely movement and temperament of the draft with a lighter breed such as a tb.
There are great points to all breeds. For eventing, and anything warranting jumping over more than just small logs or x-rails/2', I prefer a cross, and love clyde crosses b/c I have one, but also b/c in my experience, they tend to have better necks (thinner and better for riding) than belgians or shire crosses. Again though this is ONLY from my personal experience and have seen great drafts and crosses of all breeds.
I do eventing, hunters, and dressage with my 17.3h clyde cross.