Opt for a mixer grinder with more than 750 watt motor if you will grind dosa/idili batter, make spice powders and do such heavy duty chores frequently. Else, a 500 watt mixer grinder will suffice.
Power and RPM
Mixer grinders with high power will be able to sustain high RPM when grinding tough ingredients. But, low powered mixer grinder struggle, affecting durability in the long run.
blade design
Chutney jar blades should be as close to the bottom as possible so that ingredients do not lie in the gap without getting grinded.
JAR SHAPE
Wet grinding jars should have wide mouth and narrow bottom so that ingredients get drawn towards the blade for uniform grinding.
noise levels
Most mixer grinders make about 85-90dB of noise. Contrary to popular expectation, noise levels are not dependent on the power. Even 500 watt mixer grinders can be extremely noisy.
safety features
Buy mixer grinders with ISI mark as they adhere to basic safety features like shock-proof body and wiring. Also, look for features like anti-skid base, overload protection switch and lid lock.
price
If budget permits, opt for mixer grinders priced at around Rs.3-6K. They are of good built quality and often last long.