@edsu Difficulty has a lot to do w/ different margin for error. Modern disposable razors flex and are more forgiving. Safety less so, straight razors leave little room for mistakes. Bad angle/technique and you cut yourself.
Classic mustache/beard patterns coincidentally grow hair in the places hardest to shave w/ a straight razor.
I recommend learning safety razor shaving first to learn angles and technique, then move on a straight razor. Get a Dovo Shavette that uses DE blades and GO SLOW :)
@kyle thanks for the advice!
@edsu Straight razor has similar techniques to safety razors but you alternate between left and right hands, and the only thing guiding you to the right cutting angle is you, no bar or guide.
When I grew a beard last year I used a straight razor to clean up my neck/face. My best shaves are from a straight razor, but I use a safety razor normally, because of a few mishaps w/ a straight razor where I missed the angle on my chin and dug in :). I decided to stop before I got a scar.