Alex,
The S2000 is far cheaper on fuel if ran off the v-tec than the Zed. I have had one before and bought one for my mrs as her daily driver. She does try and take the zed some mornings as it is a far more comfortable place to be.
I think the S2000 makes the better convertable and has that hardtop for winter if yours is a GT?
Driving characteristics of the S2 mean that my Mrs doesnt thrash it all the time because it gets seriously loud and she find it hard work. The Zed on the other hand has good torque from low down so when she drives it she finds herself just wanting to nail it everywhere.
I think you should change as it is 100% an easier car to live with