I usually play Renegade and the Renegade option is to save the base. So I've done that more often.
I always save Wrex too though. I did kill him once to see what his replacement would be like. It was terrible. I missed Wrex so much.
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~Halo There is no Crane, only Scarecrow!
http://img195.imageshack.us/img195/3739/scarecrowq.jpg