I say the 300lb. bench press is more impressive, and more difficult to achieve, by far, especially for those of lower body weights.
In high school I ran a 4:33 mile. At the same time I was capable of a 185lb. bench press, at a bodyweight of 115lbs.
If I benched 300 at that weight, I would've been a world-class junior powerlifter. (The heavier one gets, however, the less impressive a 300lb. bench press becomes.)
But a sub-5:00 mile is nowhere near world class.
After I retired from competitive running, but still kept fit with cycling and powerlifting, I gained some muscle mass and went up to 123lbs bodyweight, and was eventually able to bench 213lbs. No way in Hell could I ever bench 300 at that weight, no matter how hard I trained for it.