From working with various editing software ranging from Windows Movie Maker - Final Cut Pro. It comes down to two decisions.
1. How much control do I want over the footage I have?
2. How expensive is the software?
3. How big of a learning curve is their with the software?
Undoubtedly Final Cut Pro or Adobe Premier, and if you can afford it AVID are your best bets when it comes to professional results. However, if your looking to just throw together some clips for your youtube video you made with neighborhood friends, then find any title on Amazon under $100 with the highest reviews. You will most likely be satisfied with just that. The benefit with emptying your pocket on the higher end editing software is your ability to grow as an editor. FCP and Premier will give you all the tools necessary to basically do anything you want. You have complete creative control, and the more you use it, the greater potential you have at having a profitable new hobby.