if money isnt that important and you can easily save up again..... i would go with the 1.4..... but if like me, you dont have alot to keep spending on your camera equipment, get the 1.8......
Personally i think unless your a professional or VERY fussy about your images, you wont notice the difference...... but like Markc says..... the 1.4 has better bokeh...... thats about it.