The production of the Model 3 will start soon, but not for average civilians - only Tesla and Space X employees will receive the first few thousand cars, so they'll be able to catch even the smallest problems and provide engineer-level feedback as fast as possible.
Theoretically the Model 3 production line is already functional, but it still needs some fine-tuning, before mass production starts. First they'll produce the simplest orders, as the first months of any production line is about quality. When everything works well, they'll add options like sunroof, second motor, special seats...etc... just like they did with the Model S/X production line, but without many of the mistakes they made in the past. Things are going so well, that they simply skipped a step in the preparations for production, as precision is much better than expected.
(Un)fortunately these two pure electric cars have almost nothing in common, as they look different, feel different, accelerate differently and have very different built-in features. In my opinion, most buyers won't have any problems deciding which one they want, as Model 3 is clearly high/superior tech, and the Bolt is more like an uglier/practical traditional car.
It seems that in the battery department, which should be the most important in any EV, Tesla has no competition, as they make the cheapest, safest and best managed (cooled/heated) battery packs. Owners of Model S/X cars report about a 10-15% range loss in very hot and very cold climates, where the Nissan Leaf, Chevy Volt, eGolf and others lose up to 50% of their rated range, as they use different battery packs and less/no thermal management.
circulating liquid coolant and touch every cell (through a non-conductive thermal pad, for safety reasons) in the pack. This relatively simple thermal management system can also use the heat generated by the battery pack to heat the cabin, which in most EVs is lost energy and/or additional stress on the batteries.
The Model 3 battery pack will be very similar, but will use slightly fewer and bigger cells, in order to cut down cost. These new battery cells are already produced in the Gigafactory on a large scale, but most of them go into stationary storage called Power Wall 2 (home use) and Power Pack (industrial use).
