Get the longer one now. Will save you from having to upgrade in the future. I do recommend a premium hitch. A standard hitch with friction sway bars isn't going to cut it.
Hensley Arrow or Propride
Reese Dual Cam
Equalizer
My preference is toward the HA or PP. Pulling performance with those two hitches is a world apart from others. Yes, it is pricey. However, if you watch your local craigslist carefully you might score a great deal (I've found three in the last three years within 50 miles of my middle of nowhere location). $800 is an average used price on them, and anything less is a great deal. I have $250 in one, and $450 in another. A friend has $800 in the third.
With the amount of miles you are going to be traveling, I HIGHLY recommend a premium hitch. Especially on the longer trailer. You will be glad you did.