are they neccessary ?

I prefer to work with dumbells and the last few weeks have only used dumbells.

This is my workout for biceps.. Short and simple..

Incline seated alternate curls : 2 x 6-8
One handed Hammer curls : 2 x 6-8

Do i really need barbell curls or are dumbells suffucient. You always hear that barbell curls is the big mass builder, or is it just strict curling in general ?