Specifically, I am wondering whether the guide blocks and the associated screw length recommendations have changed.
I had to buy a K5 when I couldn't find my older model Kreg jig. Some manuals for older jigs indicate a screw length of 1" for 1/2" stock; however on the K5 they indicate a 3/4" screw. As far as I can tell, the 3/4" screw requires the Micro drill guide. When using 1" screws on the K5, they go out the other side of the mating stock.
I have a fair supply of 1" screws. Once I add the price of the K5, the Micro drill guide, and some 3/4" screws, I'm not too far from the price of their "Master Collection", which comes with the older K3, but also includes the Micro drill guide, the HD guide, two clamps, and 1000 screws. I'm frankly not up-to-date on the differences between the K3 and K5.
So what's the deal ? Has the jig changed so that it requires different screw lengths ?
Is there a compelling reason to go with one or the other ?