Which makes a soldier stand out more from his peers: a 300 pt score or a Bachelor’s degree?

Both would make you stand out from your peers. If you are a young Soldier, you have the hardest APFT score bracket in all events. Not everyone is strong, flexible or fast enough to max out the APFT to get that elusive 300. Having that bachelor degree could be difference in getting promoted over that other high speed Soldier once you go for E7............

To answer this it really depends on many different things. For instance if you were working in a joint environment and had an Aor Force supervisor you might find that they value you having a Bachelors degree more than PT. If you’re in a unit where PT is viewed as being important than the 300 score will stand out. Overall it really depends on what leadership views as being important. For instance for me as an Air Force retiree I put more stock on education because I believe and feel that is gonna help you in the long run. While PT is good and helps, it is not as important as the knowledge one gains from going to school.

Comparing Apples to oranges- also depends on MOS- for combat arms- PT is a major consideration. For tech MOS's a degree may have more weight.

Bachelors degree

No one cares if you got your SPC with a BA or with TIS, except that if you show up as an SPC with 6 months TIS, you'll probably still be treated like a PVT. A 300 PT score will stand out much more.
By the time you are trying to get SFC, you'll want some college. I was told not long ago that practically all 11B SFC promotions went to Soldiers with two of the three: 2 years of college, EIB, and Ranger Tab. It's probably a little bit different in other MOSes.

Both "help" along with everything else listed on your PPW. You should still be able to see yours as a PV2. Furthermore, seek leadership and professional (soldiering and MOS) development courses and opportunities. Then clean up your ERB.
https://jtspratley.com/blog/promotion-point-worksheet-ppw
https://www.hrcapps.army.mil/ppw/
https://jtspratley.com/blog/army-enlisted-record-brief-erb