Here’s a bunch of posts comparing the two: The Great Debate: KA100 vs VLR
Right now the only reason to get the VLR over the KA is initial cost is lower on the VLR. Otherwise, the KA appears to be faster and possibly more reliable, though they are both pretty close. From what I’ve heard, the KA is better at most tracks by a tick, but the VLR can hang with it if the track layout allows it.
KA is big in the Midwest right now, and growing. It has the biggest grids at the regional level, a decent club following, and big national grids as well.