Practical accuracy involves the accuracy of the rifle, ammunition, conditions, and most importantly the shooter. I'll focus on three aspects of long range accuracy which I think apply most to this discussion:
1. As the distances get longer, the ability to accurately estimate wind drift over the bullet's flight becomes increasingly important (ie, downrange it's not necessarily what it is where you are). Wind drift is going to be proportional to the bullet's BC and the time of flight.
2. As distances get longer, small deviations in muzzle velocity manifest as larger deviations in impact elevation.
3. If you are shooting at unknown distances, range estimation error will manifest as impact elevation error as distances get longer. E.g. if you are off by 35 yards, a faster-falling bullet (ie, inches drop per additional yard at 800 yards) may miss the target when a flatter trajectory would allow a hit.
All of these effects get worse with lower muzzle velocities and/or lower ballistic coefficients (BCs) of the bullets.
Here is a comparison of some factory load data from those two 19.5/20" and 24" barrels, and how it will translate into downrange drop, drop rate, wind drift, and velocity. I know that handloads can improve the velocity of these loads, like a 175 @ 2700 instead of 2650, but using factory data will level out the field.
Code:
_Bullet_ _BC_ _MV_ 0 200 400 600 800 1000 | YARDS
24 175SMK 0.51* 2650 > -0.00 1.86 7.74 15.37 25.03 37.34 | drop (moa)
20 175SMK 0.51* 2525 > -0.00 2.14 8.71 17.23 28.06 41.85 | drop (moa)
24 168SMK 0.46* 2700 > -0.00 1.79 7.61 15.41 25.69 39.38 | drop (moa)
20 168SMK 0.46* 2575 > -0.00 2.07 8.59 17.36 28.98 44.41 | drop (moa)
24 155LAP 0.508 2830 > -0.00 1.51 6.52 13.01 21.12 31.32 | drop (moa)
20 155LAP 0.508 2680 > -0.00 1.79 7.47 14.81 24.03 35.64 | drop (moa)
24 175SMK 0.51* 2650 > 0.04 -0.07 -0.22 -0.43 -0.72 -1.12 | drop per yard (inches)
20 175SMK 0.51* 2525 > 0.05 -0.08 -0.25 -0.48 -0.80 -1.25 | drop per yard (inches)
24 168SMK 0.46* 2700 > 0.04 -0.07 -0.22 -0.44 -0.76 -1.23 | drop per yard (inches)
20 168SMK 0.46* 2575 > 0.05 -0.08 -0.25 -0.50 -0.86 -1.39 | drop per yard (inches)
24 155LAP 0.508 2830 > 0.04 -0.06 -0.19 -0.36 -0.60 -0.93 | drop per yard (inches)
20 155LAP 0.508 2680 > 0.04 -0.07 -0.21 -0.41 -0.68 -1.05 | drop per yard (inches)
24 175SMK 0.51* 2650 > 0.00 1.38 2.96 4.79 6.93 9.37 | wind (moa)
20 175SMK 0.51* 2525 > 0.00 1.48 3.18 5.17 7.46 10.03 | wind (moa)
24 168SMK 0.46* 2700 > 0.00 1.47 3.22 5.35 7.92 10.87 | wind (moa)
20 168SMK 0.46* 2575 > 0.00 1.61 3.52 5.84 8.62 11.70 | wind (moa)
24 155LAP 0.508 2830 > 0.00 1.22 2.61 4.21 6.06 8.17 | wind (moa)
20 155LAP 0.508 2680 > 0.00 1.32 2.83 4.57 6.58 8.86 | wind (moa)
24 175SMK 0.51* 2650 > 2650 2305 1986 1694 1435 1225 | velocity (fps)
20 175SMK 0.51* 2525 > 2525 2189 1880 1598 1354 1166 | velocity (fps)
24 168SMK 0.46* 2700 > 2700 2318 1957 1625 1335 1124 | velocity (fps)
20 168SMK 0.46* 2575 > 2575 2200 1845 1525 1257 1076 | velocity (fps)
24 155LAP 0.508 2830 > 2830 2479 2154 1855 1586 1355 | velocity (fps)
20 155LAP 0.508 2680 > 2680 2340 2026 1738 1484 1272 | velocity (fps)