Most Hercs, including most new C-130J's, can't aerially refuel. C-17s can and will. If you go C-17's, buy a comfortable seat-cushion.
My buddy from ROTC went 17s, I went 130s. While I was at Corpus training, he flew from Ramstein, Germany to Corpus Christi, Texas non-stop. A Herc would have had several awesome pit stops along the way.