Here is the EOR values for the match ups (S17)
44 v 4
....A..........2.........3..........4.........5..........6..........7..........8...........9...........T....
-0.3487, 0.8650, 1.8739, 1.6624, 2.2947, 2.1373, 1.6687, -0.6784, -1.1790, -2.0740 doubling
1.2274, 1.7366, 3.6899, 2.4351, 2.0770, 0.6261, 0.2614, -0.7280, -1.5894, -2.4341 splitting DAS
44 v 5
-0.3709, 1.6197, 2.4375, 2.1879, 2.5100, 2.0327, -0.3604, -0.7370, -1.1971, -2.0306 doubling
0.9307, 3.9645, 4.0262, 2.5109, 2.6846, 0.8223, -3.2133, -0.7685, -1.5541, -2.3508 splitting DAS
44 v 6
0.2836, 2.1548, 2.9055, 2.2623, 2.4518, 0.0505, -0.3186, -0.4856, -1.1358, -2.0422 doubling
3.7826, 4.0223, 4.0252, 2.5864, 2.6750, -2.9183, -3.5049, -0.5278, -1.3687, -2.1930 splitting DAS
As you can see for 44 v 4, the seven is a factor in doubling but the ace is factor in splitting. For an ace neutral count splitting would be more correlated to the count but for ace reckoned count doubling would give a more accurate decision due to the ace acting like a low card rather than a high card but it was counted as a high card. This makes the count a very bad indicator of the correct decision for splitting with an ace reckoned count.
For 44 v 5, the seven is most important for splitting decisions and the ace acts more like a low card again. For doubling the ace acts as a high card but seven has a small affect on the decision. Both ace neutral and ace reckoned counts have a much better correlation to doubling than splitting.
For 44 v 6 the ace totally over rides the ten for splitting and the seven is equally important. For doubling the ace is almost neutral and the seven has a small affect. Ace reckoned counts are served terribly by the splitting index. It has almost no correlation to the decision. Ace neutral counts do better but the seven still hurts the splitting correlation. Doubling on the other hand has a strong correlation for both types of counts.
In case you don't know this the rate at which gain is accumulated after the index is exceeded is a function of the correlation of your index to the correct play. A high correlation means a quick increase in gain while a weak correlation means an anemic increase in gain as the TC increases beyond the index.
It is still a matter of style but the math favors doubling over splitting except for the dealers 4 where doubling is better for ace reckoned counts but splitting is favored for ace neutral counts.