Do you think OPPOSITES attract, or is someone who is very similar to you better in the longterm?

I always thought that someone who is very similar to me would be ideal , esp for marriage and what not, and I still agree that its prob best to find someone whos core values at least are similar to you, but then i just got out of a year and half long relationship with a guy who was soo much like me, he was like my twin, thought we were soulmates. at first i was ecstatic and totally in love... but after a while,,, it was like, wow i almost feel like im hanging out with myself! we fed off eachother,he was so much like me even in his speech and mannerisms and i think i got kind of bored becaue there wasnt a diffrent energy when he was in the room or something...we eventually broke up because i needed a break from him, and now I feel like im kinda turned on by guys who are quite different than me in personality and interests and stuff.... but which do u think works in the long-term? different personalities, or very similar? is there any truth to the phrase 'opposites attract?" im confused!