Hi, I have the UK version of the Makita XSL06PT in my mitre saw collection, and I really like it.
If you were thinking about a Kapex, hold fire as the new improved model is coming your way in October I believe?
Back to cordless though, we have almost completely gone cordless with our mobile set ups apart from a table saw. I have a few Makita mitre saws, including some cordless models. The above as mentioned and also the smaller 36 volt DLS714Z I cannot fault either, the DLS714 doesn't have a laser so I fitted an arbor nut type and it works great. The dust extraction isn't as good as the the XSL06PT either but, ok.
The XSL06PT has pretty good dust extraction and is generally a decent saw albeit quite heavy. Our was pretty well set up and square out of the box.
We use the smallar saw for a lot of the work, as for it's size, it has a respectable width and depth of cut, and great battery life. For the big stuff we use the XSL06PT, and if you're buying one saw, that would be a good choice.
I have no experience of the Milwaukee saws.