I agree completely that traditional dip nibs are the only way to get really crisp, fine lines.
For beginners, there is so much to learn about the construction of each letter and the new method of putting marks on paper.
Often times they have to learn a new grip and how to reorient the direction of the paper.
It can be an overwhelming number of details to work on all at the same time.
In my classes, I found it very helpful to have an assortment of tool options so that students could see if they got better results with a parallel or cartridge pen or even a marker.
In many cases, the less complicated pen was of huge benefit in the learning process.
Some people think the marker or cartridge pen looks easier so they try it first and the results aren't very good.
So, I give them a dip pen and -voila- they suddenly do much better.
It is entirely unpredictable which people will do best with which tool.
Trying all of them is the only way to tell which one is the best beginner tool and after that, it is fun to figure out ways to make all the different tools work for you.
Markers do not get a lot of respect, but they are very useful in some situations.
I've had people show up with some slick paper intended for commercial printing and the only ink that will stick is a Sharpie Calligraphy marker.
Of course, you can't get any fine lines with the marker.
But, if they have their place cards and need the job done, it is better that I have had some experience with the marker.
No, it is not an ideal situation, but I can make it look very nice and the client is happy.
If you intend to turn your lettering into a business, I highly recommend you learn to warn any client who is providing the card stock that you do not guarantee anything until you have the stock in hand and can find the ink and tool that will work.
The other advantage of the parallel pens is that they are portable. If you practice more because you can take a fairly good pen with you, then it is a fair trade off. Getting the super fine lines is important, but putting in the hours to build your muscle memory is essential and you can build muscle memory without the lines being the finest.