Yes but those 10 units of infantry cost $30 and I get to roll TEN dice on offence and defense- giving me TEN chances at hitting. Ten offensive points, 20 defensive points.
If you spend those $30 on Tanks- you get 5. Only 5 dice. 15 Offensive points, 15 defensive points.
If the tank stack attacked the infantry stack- using LL
Round 1
5 Tank - 2 hits (1/2 left)
10 Inf - 3 hits (1/3 left)
Round 2
2 Tank - 1 hit
8 Inf - 1 hit (1/3 left)
For every Tank hit, the Infantry lost 2 defensive points (worth $3 IPCs) and the infantry still had 9/10 of its strength
For every Infantry hit, the Tanks lost 3 offensive points (worth $6 IPCs) and the Tanks have 4/5 of its strength
If the infantry stack attacked the tank stack
Round 1
10 Inf - 1 hit (2/3 left)
5 Tank - 2 hit (1/2 left)
Round 2
8 Inf - 1 hit (1/3 left -> plus 2/3 on round 1 = 2 hits)
4 Tank - 2 hit
Round 3
6 Inf - 1 hit
2 Tank - 1 hit
Round 4
5 Inf - 0 hit (5/6 left)
1 Tank - 0 hit (1/2 left)
Round 5
5 Inf - 1 hit (2/3 left)
1 Tank 1 hit (1/2 plus 1/2 on Round 4)
So both ways, the Infantry WIN on Low Luck!
Honestly the most effective force is a buttload of infantry supported by a few Tank/Fighter/Art - usually the ones you start with.
With Russia/Germany in every AA Game- I usually buy 1-2 Arm/Art and the rest Infantry every round. More units = more die rolls = more chances at hits.