I've had both a Navionics chip, and I currently use Jack's chip in my Lowrance units. I've been generally happy with it. The tradeoff you have to consider is that Jack's card will only have local lakes (Kansas and Missouri). He actually has a few more of the smaller lakes in KS than what you would get if you went with a Navionics chip. If you get a Navionics chip, you can get the whole South region that includes Kansas, Missouri, Oklahoma, Texas, etc. I never travel to those other states to fish, so I'm happy with what Jack's card offers. Detail is good, very accurate and the ability to overlay old maps on top within your unit is nice too.
"A system of capitalism presumes sound money, not fiat money manipulated by a central bank. Capitalism cherishes voluntary contracts and interest rates that are determined by savings, not credit creation by a central bank." Ron Paul