The Noveltech Character and Vocal Enhancer use similarly advanced techniques for optimizing audio simply and intuitively. So, one could use the Vocal Enhancer for instruments and the Character on vocals. However, the algorithms in each plugin are entirely different, which is why they were each designed specifically for their general purpose. They were each optimized for their task.
Notice that on the interface of Vocal Enhancer, there is a frequency graph that spans the critical range generally associated with vocals; there is also a parameter for low/high frequency focuses on adding either body or presence. These parameters are designed to be lucid enough to convey the effect of the parameters you adjust. On the Character, controls of this type are more nebulous, allowing for a more intuitive approach to a wide array of timbre and tonal types; you have three modes and a range of 'Target' to dial in a setting that works for your content. Of course, both plugins may overlap in terms of effects that can be accomplished, but they each have their way of going about it and their interface for doing so.
It's like comparing two EQ plugins, say the Mäag EQ4 and EQ2: could you treat frequencies with both? Yes. Are they both great for adding Air and transparency to instruments and vocals? Absolutely. But we recommend using the EQ4 on vocals because each band has both boost and attenuation, focusing specifically on vocal frequencies. You can use the EQ2 for instruments, adjust the bandwidth for various frequencies, and extract focused character and body with minimal tweaking.