I did a bit of research on them a couple months back before I was broke. All the reviews and comments on the variable zoom models have been poor. Generally the 1x is a reduced view of the 4x, and is not a true 1x. Your 4x is generally not a 4x either, generally in the 2.5-3.5 range.
Granted I do not have first hand experience, and those numbers came from a variety of reviews and sources. General consensus I have seen, and my own opinion, if your looking at a Specter replica, buy the 4x fixed. If you need to have 1x with 4x, buy the 4x fixed with the mini red dot on top.