The advantage of playing originals is that I always play something that is suitable for my level Although at times I try to push things.
When learning songs by others, unless you're talking highly technical stuff, I find I can manage just about anything... if I give it enough time. If I have time, I sit down, break it into component parts and make sure I get it down. If I don't have time, I may start with a simplified version, and cheat in parts... and then worry later about getting closer to the original.
Struggling a bit is not a bad thing: you only really progress when you push your comfort boundaries a little.