I'm set on a revolver because that's what I like to shoot and until I'm around semi autos for many years I just don't believe that me or my GF would feel comfortable in a stressful situation using a semi automatic.
Before I had a few guns at my disposal I was in the same position. I bought a Ruger GP100 thinking it would be ideal as our home defense handgun. That is until I had noticed my slight of build wife struggling with the D/A trigger one day at the range. It also acted as a glorified .38 special because she was fearful of the magnums. The GP100 has since been replaced with a Glock 17 which I found fits our purpose much better.
If you're worried about the semi's because of complexity, there's not much to a gun like a Glock. In a stressful situation the worst thing I could foresee happening is a failure to fire. This is a bad thing because with a Glock you have no second strike capability unlike hammer fired semi's. Luckily if you practice how to alleviate this the problem is solved rather quickly.
Obviously everyone has an opinion and I'm merely giving you mine, but I feel like a semi-auto can be a great choice for beginners. I am of the opinion that if you can shoot a revolver well, you can shoot just about any pistol well. Practice, practice, practice is a must either way.
And as others have said, you do not want to be thumbing that hammer at 3:00AM. Just ask the NYPD...