Hi! Welcome to the forums.
In terms of whether to get FCE or not is really based upon what you plan to do (which you haven't really told us
). My personal preference is FCE/FCP/Premiere/etc. over iMovie, but that is due to my needs and my preference for what I like to work with.
iMovie is very powerful, but also very different from "standard" NLE applications such as FCE, FCP, Adobe Premiere, Avid products, etc. iMovie is more geared to the home enthusiast, although powerful, it is no where near as flexible as a tool such as FCE.
iMovie doesn't use timelines, has limited transitions and video effects, limited titling capabilities, etc. compared to FCE (iMovie is more targeted to the home user where FCE can be said to be targeted to the high end home user/prosumer/pro that doesn't need the extra features of FCS).
To me sequences (aka timelines) are invaluable tools, since iMovies editing design is quite different when it comes to editing I personally prefer to not use it.
If you are going into video professionally eventually, FCE would be closer to what you would use then iMovie. Also, if you're comfortable with FCE, there is very little learning curve for moving from FCE to FCP in terms of general use (advanced features are a different story).
If all you plan to do is hobbiest home movies - you can probably just use iMovie and have a good time. If you want more control, more power, more features, plan to go into video professionally, etc. then FCE may be a better choice as what you learn in FCE is more applicable in terms of workflow to higher level apps then iMovie is. It would also reduce the future learning curve if you plan to use FCP or Premiere or some other "pro grade" application to edit with vs iMovie.
FCE will provide a bit more of a challenge to a beginner then iMovie, but if you have used an editor that uses a timeline for clip layout it may feel more familiar then iMovie. You may want to look at
Izzy Video - Learn How to Shoot, Edit, and Produce Better Video at his free FCE tutorial - it will give you an idea of what FCE is like, and may help answer your question of which will be better for you.