A vote for the cheap end of the scale, no pun intended!
I bought Arc's cheapest for X and Y travel on the mill, and a stand alone battery powered jobbie for the Z axis previously from Warco.
OK, Arc's cheapest doesn't do all the more expensive glass scales do, need protecting from swarf/coolant, and sometimes the read-out trips when the mill motor switches on or off despite having an anti-surge plug-in fitted, but I couldn't justify spending more for a better/higher quality spec for the amount of work I do.
Having said that, they all work well, do what I need, have made things so much easier to do, and were well worth the very modest cost, wouldn't want to be without them, and would recommend them to all on a very limited budget. Not only that, but when the read-out went down Arc were very prompt with a no quibble replacement, can't fault them.
Hope this helps other engineers on a limited budget!!
Chris