Just because the S13 makes more power given certain mods doesn't make it a "better" engine. With the S15 SR20 they made it a much smoother, more streetable engine, and it has the same, if not higher, potential as an earlier motor - it just needs different mods. Like you said, the S15 motor has more compression than the S13 one.
At the end of the day they are different motors. Just the same as the 4G63, the earlier ones were a lot more basic than the later ones, yet they all produce about the same amount of outright power stock. The later ones just have a MUCH bigger power band and are a lot more driveable.
To each his own. You probably rate an engine based on how much power you can get. I look at an engine in terms of how dynamic it is, more than how much power I can squeeze out of it.