I am sure there are so many opinions here, that one more will not hurt...

You are a bigger guy like me, I am 6'2" @ 250lbs, I would not get a smaller bike under 650cc, Although people make a good point about learning on the smallerbike, it will soon and I mean very soon feel underpowered and too smallfor you and you will want to trade up.

The dealer route is perfect to begin and then when you decide or narrow it down to a couple of bikes, go and rent each one for a day y or so, it will really help you fell better about the final decesion.
It really depends on you and the type of riding you do, just around town or if you are planning longer trips and even if you are planning on passengers.

I would imagine since you are on this site you want a Harley, narrow it down and get what YOU like and what YOU are comfortable on, no same in buying conservative and trading up, I think most of us have done that also

Just my 2 cents