as far as personality goes, i would go with ocellaris or monoculus every time. for color it would be Kelberi, Orino, Temensis or Pinima.. not necessarily in that order.
All cichlas are nice...I say look at members photos and you decide...just keep in mind 150 is just a grow out! And stay away from temensis and pinimas, cause you'll have to get a much larger tank in no time!!! Monos and Ocells are the most readily available cichlas...but for me Orinos are sick!!! and tend to grow a bit slower so you'll have time to save up for a bigger tank in the mean time. gl
They can get big, over 20" but like the other folks said they grow slower so you have more time to adjust to their needs. Those Pinima and Tems get huge and grow really fast. Heres a vid of my gang of 5 inchers. The ones with the gold speckles all over are wild Orinos. The smallest one is a Kelberi and the one with the bold dark smudging is a Peru Mono. Quality is not so good but it will give you an idea.