jerryc41 wrote:
If you buy the f/1.4, you'll have a lens that is larger, heavier, more expensive, and probably not as sharp as the f/1.8. You're paying a premium for that extra stop.
Try some of these comparison sites.
http://www.dpreview.com/products/compare/lenses
http://lenshero.com/lens-comparison
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx
http://www.lenstip.com/lenses.html
http://www.dxomark.com/Lenses/Compare