That is like saying we don't need any American fighters from before 1944 other than the P-40E and F4F-4. Remove the F4U-1, F4U-1A, F6F-5, FM2, P-38G, P-38J, P-39D, P-39Q, P-40C, P-40F, P-40N, P-47D-11 and P-51B from the current planeset for the American equivalent of just using the LaGG-3 to cover that entire period of Soviet fighters.
No, its like saying we don't need a 109G-10, because we have the 109K-4. One is faster on the level, the other is a bit more maneuverable.
Or we don't need the F4F-3 because we have the -4.
Performance curves for both comparisons were similar, one just traded a bit of speed for some maneuverability or climb rate.
From what I've read, the Yak-3 had a bit better handling, was slightly more maneuverable, but slower.
We could use an early Yak-9 more than the -3.