I use a fountain pen daily, well several pens, they are such a joy I have gathered many. It helps me cope with mountainous paperwork associated with my job as I love to use them, find my hand writing is easier to read and as a person with gammy hands I also find it less painful over time.
I have used Parker ink , because it is ubiquitous in the 3d shops, Lamy because I have many Lamy pens and the bottle is the very best design for filling pens - streets ahead of the other manufacturers. I bought this just because it was significantly cheaper at the time (they vary tremendously).
I have never noticed a difference between the inks particularly but there feels to be one here. It flows through the pens beautifully.