Well if you look at the product features it is clear one is better than the other, but really the only thing that makes a bad PSU (imo) is not getting the correct wattage you wanted out of it or overheating, neither of which you tend to really get with any decent company (again imo).
Yeah, that system barely breaks 250w, so the antec VP-450 is fine. You really can't go much more cheaper than $30 on a power supply without compromising quality, so you're fine on 450