Which web browser is better, Safari or Firefox?

I currently am using Safari web browser on my iMac OSX 10.6.4 with Snow Leopard operation system. Safari has been working very well for me until I tried to down-load music scores from a company in England. The company suggested that I switch from Safari to Firefox as that would allow me to successfully make the down-load. By the way they also suggested that I change my Snow Leopard ops system from 64 bit to 32 bit (I followed their instructions exactly to no avail).

Also is it difficult to switch back and forth from Safari and Firefox?

I asked them to simply e-mail me the music scores but they say no can do and offered to refund my money.

What do you think of this situation?