You have already gotten direct answers to your question, so I'll comment a bit on this "X factor" as you call it. Basically it is a measure of the "zoominess" of the lens. A 1x lens is no zoom at all, just a fixed (also called "primary") lens. The larger the X number, the more the lens can make a difference by zooming.
Why do you care? Mostly you don't. The range of focal lengths the lens can cover is more relevant to how you are going to use it. A 35-70mm zoom would be used in very different situations than a 150-300mm zoom, although both are "2x".
What the X number does tell you is a rough measure of how much compromise was made in the lens design. Everything is a tradeoff, and zoomability is not free, both in $ to allow for the zooming and in optical quality. All other things being roughly equal, a 2x zoom will have better optical quality than a 8x zoom. Of course other things are rarely equal. There are things lens designers can do to get better optical quality in zoom lenses, but those cost money, may lose light, cause more internal reflections, limit the aperture range, etc. These can be mitigated to some extent by throwing money at the problem, but eventually you hit other limits due to physics or the available construction techniques.
The main message is that while high range zooms are nice to use, they have other drawbacks. You have to consider how much the flexibility and adaptability of a zoom is worth it to you in various situations. Just blindly going for a high-X zoom because it will solve all your problems ignores a lot of the issues.
I just re-read this and realize that it may sound somewhat against zoom lenses. That is not the intent at all. They have their place, as do fixed lenses. The lens I probably use more than any other is a zoom, but I also own a number of fixed lenses, in fact more fixed lenses than zooms. The point is to be aware of the tradeoffs and chose the right tool for the situation accordingly.