These are all big girth related
Disadvantages?
1) Big girth = no anal. The only time a girl has even brought it up with me she was wasted and the next day said "no, no, no, no, no, no" etc.
2) Oral = Teeth. Try to get your mouth around a toilet paper tube, then take it all the way into your mouth. good luck and if you can without gagging or grinding your teeth down it, you should give lessons.
3) No Extended sex. Almost every girl I've been with has begged (begged might be the wrong word but illustrates the point) me to cum after 15-20 minutes of sex. The few times it's gone longer than that have involved a lot of alcohol. I'm all for foreplay, going down, making her cum first, etc, but as a general proposition, women don't like being drilled for hours on end. That goes even moreso for thick cocks. I love the bump and grind, switching positions, getting her comfortable, but i have heard "are you close?", "please finish" and "I'm getting sore" enough to know that even if they like big cocks, there can be too much of a good thing.
Advantages:
1) The way she inhales as you start pushing in. I've been married for almost ten years now, and one of the memories that I always have is the look on a partners face as I push the head of my dick in. Nearly every partner I've had inhaled deeply when I first started to enter her, and in my memory I still love that sound.
2) The hand on your hip. You've been making out, things are getting hot, as you start to enter her she puts her hand on your hip. She want's you to slow down. Not slow down because the relationship is moving too fast. Slow down because your cock is too big and she needs a little time to relax and take it in. My favorite memories include the first time I had sex "whoa, easy big boy, I'm not used to so much", a one night stand I had "oh god, big, big, big, big...etc" and my now wife "oh my god, you're not even half way in yet are you?"
3) For those of us that have sex with women/men who already have boyfriends: "You've got a big dick. It's bigger than my boyfriends." I've been married for a long time and didn't really get around in college. But one of the hottest things I experienced was fucking a girl who got off telling me I was bigger than her boyfriend. (Full disclosure, she came to my house, I shut her down b/c she already had a boyfriend {aren't I nice} then she tracked me down at a bar and I figured she really meant to cheat on him. Anyway.)
It took me a long time to actually realize that I have a big cock. i don't have big length but my girth puts me in a rare group. Are there disadvantages to having a big dick? Sure. But there's no way in hell I would trade my cock for a smaller one. I might trade some girth for length, but at this point it's just semantics. I might never know what anal sex feels like, but my wife knows what its like to be fucked by a really thick cock, and I'm happy to give her that feeling whenever I can.