I think it really depends what you want to use your pen for. 
If you want it just for signatures, I would get a pen that has a broad nib. 
If you are using it to write a lot, you will have to experiment. 
Depending on your paper, you will have to change the nib sizes. 

Satosora

I picked up calligraphy recently and found it a very relaxing art form. Besides that I never used them, but there is a whole world to learn about different styles and purposes behind them. What do you use them for?