Your best bet is to look in the diy prom faq for more info.
It also depends on what you want the data for and how much you want to spend. I have an auto xray handheld scanner from ebay I got about 7 years ago for $90 and it tells me all the info I need plus datalogs 16 seconds worth of data, but it datalogs slower than the pc programs.
A laptop is more cumbersome driving around vs the handheld scanner, but you can do more with it. The laptop screen is hard to see in sunlight also and you need a good battery or a ac-dc power inverter to run it in the car.
All of this depends on what you have now and what you need it for of course.
