Hypertech vs Superchip programmers

Is there anyone who has any experience with the Hypertech or Superchips computer programmers? I've been thinking about getting one of these programmers for my '98 Ram. Not only for improved performance, but also because both claim to be able to adjust the speedo for tire and gear changes. Hypertech is a name I'm familiar with, and they claim about a 20 ft/lbs gain in tq and 25 hp gain. The superchip product is new to me, but seems to have most of the same features and they claim a gain of 46 hp and 59 ft/lbs of tq. That sure sounds good to me, but I didn't think you could get that much from just a chip. Any input will be greatly appreciated!