Ok so here is some feedback on the Milescraft version of the drill guide. First it is mostly all metal which is better than some of the others which are moulded plastic but the footprint is too small which makes it unstable and with the spring fitted not very managable unless you remove the spring, this might be because there is only one spring on one side or it could be less powerful. The base actually sits on four little rubber feet that are there to stop it sliding but this does not help with accuracy as it can tilt from the vertical, not much but over the distance it makes a difference. One solution that might help is to pop out the four rubber feet and fit a wooden base to give it more support and possibly also clamp it down but doing this makes it pointless for my job of drilling countersink holes because the idea was to reduce the time needed by having a fixed depth and portability without the clamping. It is also worth pointing out that the depth stop is a really cheap bit of plastic where I doubt the thread is going to last that long, it really needs a better clamp to go round the 14mm support leg.
Another idea that would make it very usable would be if it had a wider base attached which then sat on two tracks that were clamped down, now it would slide along into each required drill point.
So my conclusion is that yes the more expensive Rockler / UJK version could well justify it's cost but I cannot say for sure as I have not handled one, in hindsight I would not have brought the Milescraft version.