the OBS will have the same engine as your coupe, so don't expect it to be any faster, and it will have the same ride height, and some more room in the back obviously (however the rear interior is kinda narrow, lots of plastics in the way).
The forester has a 2.5L engine, sits higher from the ground, has bigger tires, has a higher roof line, and just overall has a lot more room inside. the dash is the same as the 98-01 impreza
however, if you are leaning towards the forester, go for an 01 instead of an 00. the 01 got a mild redesign of the front, rear, and sides (interior is pretty much the same) and you could get the S model in all white or all black (instead of the 2tone), and its a great starting platform to make an awesome looking car