It's probably not worth talking about it on a forum dedicated to one of the two brands

, but personally I think it depends on your priorities.
Things that I like more on the Volt Premier (keeping in mind that I've only played with a showroom Model 3):
- Google Play Music / Apple CarPlay are available and really awesome (but I am nervous about long term support / improvements)
- Hatchback
- Interior finishes - this will be contentious, but I prefer the leather work in the Volt, the wood accents are certainly pretty nice on the 3, the plastics are moderately better feel/finish on the 3 so it depends on your priorities, I care about the leather feel more
- I like buttons for some things, I know I know I'm wrong

- Tow hitch available (although trailer towing isn't warranty supported AFAIK)
- More affordable out the door, probably more affordable with any reasonable real cost of ownership comparison
- Repair availability
Things that I think are better on the Model 3:
- Electric range (duh)
- Performance and handling (duh, but just guessing from reviews)
- Both interior and exterior styling (duh)
- Assisted driver functionality (duh)
- Built-in software (duh)
- Options options options (though expensive)
- More storage space (though less contiguous)
- Better for long loads
- Back seats are better but still uncomfortable for adults
- Longer term software updates (GM uses it as a cost center)
- I frankly hate all the brands involved in the Volt: GM, Sirius, and OnStar
Important things I don't know about:
- Road noise
- Sound quality
- Phone use
- Long term reliability