I'll make a comment about measured precision and actual accuracy.
When selecting measuring equipment for your machinery consider the accuracy your machine is capable of and the repeatability. Most machines that we use use are are anywhere from 0.001 to 0.006 on average whish is good enough for about 99.5% of anything we do. Yes we can increase that by approaching from one direction only but how many do or know to do so. Even then eyeball estimation we get down to a tenth to 3 tenths. Good enough for about 99.98%of what we do.
How does this effect or selection. Easy, pick the cheapest that has the best repeatability (very important) with a precision of about 0.0001 to 0.0002 and you should be good. Second is waterproof (greatest water resistance) gives the advantage flood cooling (believe that everyone should add despite the mess issues as it greatly improves finishes and avoids using toxic oils and coolants, which eases parts cleanup) along with ease of custom fitment.
The consideration for DRO's is, is it for production (heavy long term use) or ease of use (careful long term use)?
Given this it should guide you as to the best selection.
Electronics well here it only becomes quality and if you want to interface it with something else.
Finally, if you plan on going CNC (definitely worth the money) don't waste the money or effort, skip DRO, a good servo or hybrid stepper systems provide measured DRO readings from the devices (I would recommend Teknic Clearpath SDSK servos here, power and accuracy) into the CNC display.