Might vs. Attack and Life Stars

Troops
Tier       Might    Attack/Life   Ratio Tier 1       4           1         4-1   (best) Tier 2      16           2         8-1 Tier 3      24           4         6-1 Tier 4      72           5        14-1 Tier 5     144           ?

Walls
Tier      Might     Attack/Life   Ratio Tier 1     18            1        18-1  (worst) Tier 2     24            2        12-1 Tier 3     30            4       7.5-1 Overall Ratios, Best to Worst Troop T1   4-1   (best) Troop T3   6-1 Wall T3    7.5-1 Troop T2   8-1 Wall T2    12-1 Troop T4   14-1 Wall T1    18-1   (worst)

The higher ratio means that in an attack, for a single attack/life point you lose or kill more might. Lower ratios mean that for a single point of attack/life, you lose or kill less.

These attacks asssume all boosts and heroes are equal, and type (foot, ranged, mounted) are equal

Examples:
Attacker:   1000 T1     1000 attack points    if all killed, lose 4000 might

Defender:   250 T3      1000 life points         if all killed, lose 6000 might

total kills ratio for attacker is 1.5-1, benefit attacker

Attacker:     1000 T1     1000 attack points    if all killed, lose 4000 might

Defender:     1000 T1 wall  1000 life points        if all killed, lose 18000 might

ratio for attacker is 4.5-1, large benefit for attacker

Attacker:     250 T3         1000 attack points      if all killed, lose 6000 might

Defender:    250 T3 wall   1000 life points          if all killed, lose  7500 might

ratio for attacker is 1.25-1, slight benefit for attacker

Life benefit by type to defender
Defenders have an automatic advantage when the type of attacking troops is defended by a type stronger than the attacker.

Example:

Attacker:  1000 T1 foot

Defender: 100 each T1 foot, ranged, mounted mix

The ranged will defend first since they are strong against foot. Not sure what the "strength" ratio is, but this generally gives the advantage to the defended, unless there is only 1 type of unit defending. Then the attacker can choose the type stronger than the defended and have an advantage.

This defense advantage will affect all of the ratios listed above, generally giving attackers a more balanced ratio.

Other boosts
The level of an attacking hero, Combat Runes, and Rune of Fury increase the attack points of the attacker.

The level of a defending hero (assigned to Training in same city's Great Hall), Shield Runes, and Rune of Invulnerability increase the life points of a defender.