I voted for bath. Only becuase if you ever want to sell i think you need a bath more than a shower.
But i shower.
Not so the case anymore. I've 'converted' quite few up here in the wee village of Londinium, many one and two bed flats are happy to have a nice walk-in shower instead of a bath, and it doesn't affect value.
It's when you get up to family houses that it's important.