I'm still not clear on the question - did you mean, why would you want more than one expression pedal, or why would you want more than one EV-1?
On the first question, I use 2 expression pedals - how they are used depends on the patch - they could be volume, wah, or wah, and amp morphing, etc.... I seem to always have a wah block controlled with an EV-1.... the function of the other pedal varies. For the gig I'm doing now, I couldn't go to one pedal - that would give up too much function. Conversely, I don't think I need three. If I was only playing in the studio/bedroom, one would probably be enough.
As far as quality, the EV-1 is great, as are some others ... whether you would want to mix brands in your rig is pretty subjective and at the close of business, a matter of taste.
