Its a very good question.

Here is a comparison of the two products, HP Tuners and EFI Live:
http://mysite.verizon.net/whenn1/HPT...LIVELS1LS2.pdf

EFI Live has reduced the price on their product but it still cannot support any of the newer ls2 based vehicles.

Any interface you buy from HP Tuners can support every vehicle we list on this page:
http://www.hptuners.com/products/vcmsuite_vehicles.php

Hope this helps.