Haflingers are great sturdy breeds but most of the breeding now of days is done for ''light'' style breed which is really a pity, plus they tend to run on the short side and he's kind of tall to be riding a 14.3hh horse. :)
I'd surely say a Fresian due to their conformation and abilities to carry weight over time.
Percherons are nice but surely run on the tall side!
Belgians would be a good idea. They are shorter as mentioned, but very sturdy.
Suffolk horse is a very beautiful draft, they don't have the feathers like most other drafts and they have a very elegant look with a lot of strength. They are actually really not that common, and kind of expensive but it'd be a worth while investment! 8)
Shire's were not mentioned. They are very nice breeds, similar to the Clydesdale but with slightly different conformation and colors.
Its not so much the breed of horse but more or less its size. Im 5'11" and still look tall on an 18hhish Percheron. If you are larger (whether bu muscle or weight) Just look for a sturdy horse. I mean you wouldnt get a piggy back from someone half your size right? Just like you wouldnt pick a shetland to ride.
Generally heavier set breeds (Belgian, Clydesdale etc..) are a good choice. If you can find a Draft cross (ClydexTB) Then you have a lighter, versitile horse but with a bit of bulk.
Avoid breeds that are known as light weights (etc arabians) I saw alotta people who mention Freisians, that would work definitely.
Bascially don't be too picky bout breed just look at the build and height of the horse. If they look strong enough to carry you...well there you go!