I get asked on weekly basis what the best editing software is. There are a few options worth considering and what you choose will depend on your specific needs. The top three that I recommend cover all bases, from beginners to experts, and Mac's to PC's.
The first and most widely used software is Adobe Premiere Pro. It's the gold standard of user-friendly, professional grade editing software. It works on both Mac and PC and your subscription will allow you access to both. It has all the functionality I've ever needed and the best part is that it's constantly expanding. The relatively new Lumetri Color grading panel is a particularly useful feature that helps with making a fast turn around and efficient workflow. Being able to do everything ‘in house' is great. It's a little on the pricey side at around $19.99 per month but if you're serious about wanting to make videos then it's worth considering.
Final Cut Pro X by Apple is also a contender, although over the past years popularity has dropped significantly. FCP gained a reputation for favoring amateur productions like skate and surf videos and as a result a lot of the professionals went to look elsewhere (including myself). The software also only works on Mac's so this might not be an option for those who prefer and own PC's. If you're a fan of the Mac interface then this software has all the user-friendliness that you'd expect. It handles 4K video footage better than other software on comparable machines because of how it renders and manages background files. Overall Final Cut is easy to get to grips with but at $299.99 I recommend beginners test the water with Premiere Pro first. Ultimately both software are great for learning the fundamentals of editing, but Premiere will be more beneficial as you begin to demand advanced features.
For those who don't want to spend any money at all, iMovie is a good option. As you might expect with a free piece of software, it's targeted at beginners and doesn't have as much functionality as the others. You can get the basic editing functions down with little or no past experience, but ultimately you won't have much flexibility and some of the stock options look amateur (titles and transitions, etc). If you're looking for something accessible and easy to use, this could be for you.
Bonus: If you want to have some fun editing on your phone, check out Premiere Clip. You wouldn't expect to be able to edit on a phone but this one might take you be surprise. Combine it with an app like Filmic Pro for advanced mobile camera controls and you have a great ‘mini' setup. There have even been award-winning feature films like ‘Unsane' shot entirely on the iPhone!