Which Generations Prius are best ? What years ?

The first owner wins - he gets a trouble free 150,000 miles and saves money on gas. After that a low cost Prius really is not when you add $2500 for a battery, $2600 for a brake booster and hundreds more here and there.

The mpg advantage over a Civic or Corolla is lost through repairs.

Low cost and reliable that can be fixed with Autozone parts?
Honda Civic (2012-2015)
Toyota Corolla (2014-2016)

 

replacing cells is playing whack a mole. some have had decent success just replacing them, others have had success replacing and balancing, others have had success replacing, balancing and balancing the whole battery. and many have had failures.
a new oem will last at least 10 years 99.999% of the time.
it really depends on what you're trying to achieve, how much you want to spend and how much your time and convenience are worth.