i know that this may depend on what year it was made in...also which would be a better buy

X5 definetely,,,,theres a possible V8,,more spacious and more car for your money

In my opinion the X5 is a better buy. Sure its more expensive, but you get what you pay for. The X5 also has an optional V8 if that is what you want. Also in my opinion the X3 is just not a good looking vehicle. You should also consider that the X5 was recently remodeled while the X3 is starting to show some wrinkles. As far as which one is faster, I really can't tell you because it is hardly relevant when comparing these vehicles. Neither is really fast nor slow.

If speed is really your thing though than you might want to wait for the BMW X5M that is set to debut at this year's New York Auto show. This along with the X6M will become the top performance SUVs from BMW and are sure to give the Porsche Cayenne some much needed stiff competition.

Hope this helps.