Ok, I'll give you my take on ports. I've only had the one, so my knowledge is limited, but here it goes...
1) needle size -- this depends on what drugs and how big of a needle you can tolerate. I use a 20G, which is kinda big, but definitely tolerable.
2)Pain when accessing -- I use emla. I know several people who don't use it, but I figure if I don't have to have pain, why do it? I also change the needle myself, so in order to place the needle I need the site to be numb to trick my mind a little.
3)the hole -- well, the actually needle hole when you pull it out isn't that large. I have a pediatric port and the port itself is about the size of a nickel. and my incision site was about an inch long, but the scar's only 1/2 inch now.
4) can you see it under the skin -- I had my port placed in my shoulder, right in the bend near the armpit. When I have my arm hanging at my side you can't notice it at all, but if I have my arms behind my head it pops out a little. I like the placement I chose since I can wear any type of top and I don't have to be timid when I'm in the hospital with a male nurse. I know of several females who have it in their chest who like it and a few who have one in their thigh and have done well with that too.
5)sore when touched -- My port is still tender at times. Usually around times that it's been recently accessed. Typically it takes a pretty good hit to make it hurt though.
6)inconvenience -- You have to maintain the port with monthly flushes, which sometimes are hard to keep track of, especially if you are on frequent IVs like myself, making the month date change constantly. Also, you have to have the needle changed weekly, but that isn't much different than a PICC (bonus though, you get some time to take a normal shower without all of the bags and tape and water-sealing nonsense every week.) But the needle stays in the whole week, and then you take it out and put another in. Other than that, they're pretty nice little gizmos
7) seeing through clothing -- Never had to really worry about this one. Sometimes my tubing pokes under the sleeves of my shirt, but that's just because of where it's placed.
8) longevity -- My port is 4 years old and starting to get sluggish. I think I maybe have another year to it, 2 if I'm lucky. I've heard of ports lasting 6-8 years, but the trick is taking good care of them. ALWAYS be picky about how clean your nurses are when it comes to sterile procedure. It'll really help a lot to keep the port longer.
Hope this all helped... If you have any more questions feel free to ask!!