I've used many, many pens along my art filled journey and I do have my favourites (mostly all of them) but it can be very confusing when you are first discovering pen and ink drawing. . . what pen will work best? I'll tell you what I've learned so far. . .
When doing line work you want a pigment ink over a dye based ink, it is waterproof when dry so if you decide you want to add watercolour or coloured marker later it won't smear or smudge.
Pigment means: "a dry insoluble substance, usually pulverized, which when suspended in a liquid vehicle becomes a paint, ink, etc." according to Dictionary.com
Does that help? No? OK, let's go a little further.
Currently I am using 4 different pigment pens: Pigma Micron by Sakura, Staedtler Pigment Fineliner, Copic MultilinerSP, and Faber-Castell Pitt pen. A side note: I also use Prismacolor illustration markers but not for line work as the ink is water resistant not waterproof.
Sakura Pigma Micron states that pigment ink stays on top of the paper where dye based ink penetrates into the paper. It is much more stable due to the fact that pigment molecules are 100 times bigger and chemically more complex therefore less susceptible to UV rays, chemical degradation, pollution from contact with oils and other chemicals on papers, etc.
The Staedtler pigment fineliner is one of my new favourites, the description says: Pigment ink, indelible (in accordance with ISO 14145-2), lightfast, waterproof
Copic states that their MultilinerSP is, like the others, waterproof, archival and photocopy safe though these pens have an aluminum body, replaceable nibs and ink.
The Faber-Castell Pitt pens are little more unique, they are India Ink. . . also waterproof when dry, archival and ph neutral.
Wikipedia describes it this way: Basic India ink is composed of a variety of fine soot known as lampblack, combined with water to form a liquid. A binding agent such as gelatin or, more commonly, shellac may be added to make the ink more durable once dried. India ink is occasionally sold in solid form (most commonly, a stick), which must be moistened before use.
All of these pens are excellent in my opinion and I use them regularly depending on how I feel that particular day. You must try them all to find a favourite as some react differently with the type of paper you are using. . . and it's a known fact, you can never have too many pens.
I hope this has been useful and please don't hesitate to e-mail or message me if you have any further questions, I will do my best to help.
Happy pen hunting.