What are you referring to by electrical assistance? Apart from DCCD on the STi there's not much difference on the electrical front on the newages? I think the clocks have a shift beeper and the WRX's don't.... or are you thinking about the newer stuff that came in with the hatches like SI-Drive etc?
Differences.... there's a lot to be fair. Styling is different on each shape, engine/gearbox different, suspension different, interior different and so on..... Google might be best!
I'd be cautious about saying the 2.5 is fine as long as its looked after - there have been plenty that have failed when they've been looked after at standard power - hopefully you've got a good one! Personally, I'd go for the 2.0 over the 2.5 - it might have less torque but it makes a better car to push on track etc. Its all down to preference and you won't know until you drive one i guess
For me, the blob STI is the best of the breed (from a UK model point of view). 2.0 litre JDM hawkeye would be pretty tasty though
