A few months ago, I was deciding between getting a '98 Impreza GT or an Evo IV with an Evo V engine.
I ended up going for the Impreza. The Impreza had been one of my dream cars since I was allowed to drive one in 1999 for the first time. I lived in a place where rallying was very popular, so all my friends and I adored this style of cars; not too big, bulky, big air intakes, light, loud, rally winner. I used to have a Renault Clio Williams and a Lancia Delta HF Integrale too, two other of my other all time favourites.
Then I had some money to buy an Impreza but I was seriously considering an Evo because they look so fucking brutal and are something much more special than an Impreza, but reading a few "Evo or Impreza" forum posts I learned that apparently the Evo is much more expensive to maintain, because for example you need to change some differential fluid every 4000 km, also spare parts are much more expensive of course, because the Evo was built in much lesser numbers. Apparently insurance is more expensive, too.
What the forums did agree on is that the Evo is a much better base for tuning and is easily tuned to 400 hp, while the Impreza GT like I have seems to only yield around 300 hp when tuning on the cheap, i.e. no different turbo, no different injectors, no forged pistons, plus the gearbox can only withstand around 380 lb of torque. Ten years ago, this would have had me going for the Evo, but honestly the power my Scooby has with just a 3" stainless steel exhaust and a mild remap is more than enough for me. I live in Germany and all, but Scoobies are just not made for the autobahn and it's no fun driving at 200+ km/h all the time. I don't even know how fast my car can go... But I loooooove this car on twisty b roads
TL;DR: The Evos were really awesome cars, it's a shame they are not building them anymore. Maybe they would not have been able to meet expectations with new, more strict emission laws and would have been too expensive to develop further.