I tend to think the RB20 is "stronger" as in you can lean on it more. RB25's can have ring land problems with upped boost + detonation. Both are strong, overengineered engines though!
Given the RB25 is half a litre bigger it's obvious you can get more power and more torque from it.
Personally I like the character of the RB20. It seems to enjoy revving a bit more than the 25, and IMO sounds just a bit better.
a 200rwkw+ RB20 will have a decent sized turbo on it so it'll be pretty flat until it comes on boost and then it'll rocket off. Just bargain on having a 2L motor at low RPM. It won't be fast until you get up it, so it depends on your definition of "streetable". If you don't mind on/off behaviour and will drive it around off boost then that could work. If you want something in the middle though, it gets to be a bit of a pain. Even in my car it makes too much fuss trying to accelerate at a medium pace - it really wants to have the throttle nailed so it can do its thing