I used to use final cut pro on a macbook Air and it wasn't that bad, but was kind of slow with the amount of footage I was editing. So, I went out and got a PC built to use Adobe Premier since I heard good things. Turns out Adobe is WAY slower than Final Cut pro on a laptop that has 1/4 of RAM than my PC. I know Premier is a lot more complex, but wow is it unbelievably slow to render videos imported. The footage I imported is a little over an hours worth of film and shot at 1080 resolution. I have plenty of memory space to utilize, so not sure what other troubleshooting I can do in this situation. Might have to go back to final cut pro.
In terms of software optimization it's going to be hard to beat proprietary Apple software on proprietary Apple hardware. It's all literally built to only work with each other in the best possible way, so in that sense you might be a little surprised at the performance you can get out of lower end hardware.
FCX holds your hand more than Premiere when it comes to understanding the technical aspects of video editing and media. If you are importing unoptimized media into FCX it's going to basically optimize it for you behind the scenes so that you have a good playback experience. In Premiere you would have to do it manually or set it up to occur on ingest, but either you way you need to at least understand what that process is.
One the biggest knowledge gaps for people is understanding media. It has a HUGE effect on performance and stability, and while Premiere lets you throw all kinds of different types of media together in one timeline, it doesn't necessarily mean that it's all going to perform great. Some video codecs are optimized for video editing, and some are not. Understanding what you are working with can help you understand why you're getting the behavior that you're getting.
The above said, it doesn't mean that there might not be something going wrong. Look at the other advice already offered. But so often it comes down to the media. All editing software has its different pros and cons, so maybe FCX is for you, but if Premiere generally had terrible performance for everybody, it wouldn't be used professionally. The blessing and the curse of Premiere is the low barrier of entry. You can make it pretty far and be creatively executing what you want without understanding the technical aspects of video editing, so you end up with a lot of people confused about performance.