If you are interested in alternatives to Arduino/RAMPS, take a look at 32-bit controller electronics. They have much faster processors (e.g. 120MHz ARM Cortex M4 in the Duet WiFi and Duet Ethernet, see duet3d.com), so processor load isn't an issue. They nearly all have firmware-settable motor currents. This is well worth having IMO: no need to twiddle ports while looking at a voltmeter, or setting the current by trial and error, you just set the current to what you want e.g. 75% of your motor's rated current. The motor currents can be reduced by the firmware at appropriate times, for example when homing or when the motors are idle.
Thermocouples are typically more accurate than thermistors, but PT100 sensors are better unless you want to measure very high temperatures. With a thermocouple, you need to run thermocouple wire all the way back from the thermocouple to the interface board, to avoid temperature errors. This makes it hard to have a connector on the print head for easy hort end removal.Thermocouples only generate a few millivolts or even less, so the wiring picks up interference by induction easily.
The Duet WiFi and Duet Ethernet have daughter boards available providing digital interface for thermocouples and PT100 sensors. The chip on the PT100 board is specified for +/-45V over-voltage at the inputs, so a short to 24V should not cause damage.
32-bit boards offer have other advantages soo, such as firmware configuration from a test file (no need to rebuild and re-upload the firmware to make configuration changes), and the better ones provide a web interface via Ethernet or WiFi.
The reality is that 8-bit controller boards such as Mightyboard are long obsolete by current engineering standards. But Arduino/RAMPS is still widely used because the Chinese-built versions are so cheap.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].