Here is a story: Watching a friend play for the first time, I noticed something quite nasty. Each and every single time he was in human form, he was invaded by douchebags with gears way ahead of what you were suppose to have at those levels. Ok, one encounter of that kind could be interesting, but no. Every single time he was in human form, someone with advanced gears invaded. And to make things better, when he tried to call for help he: got failed summonings, got killed by the invader before getting help or summoned players without proper gears to face the invaders. To make things "better" , the few times he managed to summon someone "strong" enough, he wasn't invaded.
I went home and I tried to replicate the experience, (new character following the "normal" route) and I found the same thing: If I was in human form I was getting invaded, without fail, by people with gears way ahead of the place.
Considering how rare the humanities are at the beginning of the game, If you are a new player, I think it's safe to say that it is not recommended to play in human form. Seriously, looks like there is a legion of douches hunting down new guys.