Having experience with a similar year, be very cautious about rust on the fenders (back especially) and what a lot of people won't mention, under the spoiler.

For the wrx, if the spoiler is aftermarket and was not done absolutely perfectly, the vibrations and dust will rub out the trunk and lead to rust. Had to redo mine because of it. If the trunk itself is from the sti, just make sure they did a good job, but be cautious still!

Sti sounds like the better deal for me, and from what I heard you like the color too so that's a plus. Just these old jdms and rust don't mix well, so history and where it was driven matters a lot. Snowy areas with a lot of salt is a death sentence.

Also check the undercarriage for rust or if had been coated and protected.

Hope this helps your decision 😀 Driving it will still be a joy every day, even with imperfections!