Not sure how you can say the 1.4 is just as good as the 1.8, it just isn't!
The 1.4 will give you 2/3rds of a stop more light gathering and if used at 1.8 will be much sharper than the 1.8 is at 1.8!
The build quality is also better, optically I find the 1.4 sharper than the 1.8 and I have...