Based on usability alone, it's not even a competition. The biggest hurdle is getting people to change their ways. Last time I checked more people used yahoo mail or hotmail than gmail.
Luckily, anyvite has built in advertising (of the the Anyvite product) any time someone uses it to hold an event.
I never use Evite (no one evites me either) so I may not 'get it'. But I don't think anyvite necessarily needs to get people to switch (though maybe declaring war is probably good for PR).
There is potential in the many people who have never used evite. I think anyvite has more of a chance for after work drinks or meals (maybe you need to reserve a table) an other casual & short notice stuff like that. It's probably good timing for a second wave of this kind of thing as mobile internet is getting a critical mass.
