I have tried both many a time. There used to be this amazing spray tan place about 20 minutes from my house. I LOVED it. I came out even, dark, gorgeous.... plus the place made it like a spa experience. But, that place went out of business (I cried). So I went to Palm beach tan to try their Mystic Tan.... and it didn't really make me that tan. I used the darkest stuff they had and I really wasn't very dark.
So I'm sticking with self-tanner right now. I love L'Oreal Sublime Bronze (not the gel though). It's a lovely color for me and never streaky. I do miss the old spray tan place tho because it was so much less work than putting the tanner on yourself.