Toon power is based on modified stats the mod provides skewed to HPs.
Crew ship power is based on the mod dot level and the mod level. 4 dot lvl 15 is about the same as a 5 dot lvl 12, which is also close to the same credits it takes to lvl the mod.
Power does matter, as an indicator but not necessarily an indicator of strength.
If you see a team with 38.5k power, you know they aren't fully geared/poorly modded. If you see 45-46k they are probably all G11, if you see 50k they are running a very tanky team. If they are running a mirror team, power is then relative and does indicate strength.
People also tend to target the low power teams.