Every video editing application is different in a sense that there are different features, it is not that you cannot achieve the same results with other applications.
iMovies is not that feature rich as Final Cut Pro X but if you don’t need those kind of effects then iMovie is good enough.
For more serious work there are several video editing applications are Adobe Premiere Pro, Final Cut Pro, Avid, Davinci Resolve but the best application is the one which you have, know how to operate and is intutive to bring your visualization live.
I use Final Cut Pro X because I have Apple operating system, I get all the updates, over the years I have become comfortable with it and still learning. For me Final Cut Pro X is the best app for video editing since I have learnt it, I can visualise things and Get the desired results.
Buy any application as one time purchase. It will be good in the long run. Davinci Resolve is a free application if you decide for it. You have to pay for studio version.