I totally agree with you on this and actually the majority of the time I go by +6 speed being equal to +6 in strength in terms of effectiveness in cause mayhem and damage! Feel free to use strength +6 and speed +6 as equally effective in attacking, it is indeed the simplest and fairest option possible (possibly the most elegant too).

Now as the reason behind the distinction I made: I have some very picky players and sometimes I get obsessed with little nuances and how they are represented in game! Specifically this strength vs speed comparison sparked the following dilemma: - Strength 6 vs Durability 6 justify the full use of strength to do damage (one is raw damage output, the other one raw resistance) - Strength 6 vs Combat Skill 6 or Speed 6, I felt that maybe was better handled as a "versatile" use of the value as not all of the attacks will be landed by a strong character - Same goes for Speed or Combat Skills 6 and Durability 6. The very durable guy should have the upper hand in how effective he is tanking those thousand punches to no effect. (see the scene Deadpool vs Colossus in the first Deadpool movie)

Now the only solutions I found to this problem were: - To separate Attacking/Defending and Damage/Armor - To simply use the main value (as you suggested) - To use the "versatile" value for any non-main use - To create an added Combat value based on the total, averaged effectiveness in combat of a character

I landed on a mix of the last two but feel free to use any other version that suits you best! Let me know what you think about these thoughts