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.

 

Many of these things are manageable for a DIYer with a garage and basic tools. And it provides an immense amount of satisfaction. The car isn't hard to work on, and parts are readily available. Get some dirt under your fingernails and drive the car until the wheels fall off.

I bought my 2012 at 90k, sold it at 135k, and bought it back at 208k. It has all the issues that you mentioned, but I think the experience has strengthened my trust in Toyota. They covered the brake booster for me as the second owner and covered the inverter for the third owner. I replaced the intake, replaced the PCV, added oil catch can, and cleaned the EGR at 220k, but still may be looking at a head gasket replacement soon. In the meantime it still gets 55mpg with 50% original battery capacity.