Depends how accurate you want things to be I guess, but a 6" Wampa would be significantly larger in such a small scale than a 4" Wampa... When you get into scale at that size, small things make big differences. Like speederbikes, or snowspeeders, for instance. Some folks didn't mind the vintage molds on those, but the reality, especially to people who pay close attention to scale, is that they were grossly oversized.
The Wampa would be kind of a similar thing. Some people may not care, but if scale matters to you, it'll be noticeable.