My Str = 13 / My Dex = 20

I have a regular spear with base damage of 80 and Str bonus of C and Dex bonus of C

I have the Winged Spear with a base damage of 86 and Str bonus of D and Dex bonus of C

Now when I compare the two the Winged spear has a Stat bonus of +29 while the regular spear has a stat bonus of +27. Shouldn't it be the other way around since the regular spear has a better Str bonus and the same dex bonus as the Winged Spear. The only other difference in the two weapons is the weight, the Winged Spear being 1lb heavier. I'm trying to figure this letter thing out so I can best match my stats with the weapons I have and the ones I will hopefully obtain in the future.

I have a regular spear with base damage of 80 and Str bonus of C and Dex bonus of C

I have the Winged Spear with a base damage of 86 and Str bonus of D and Dex bonus of C

Now when I compare the two the Winged spear has a Stat bonus of +29 while the regular spear has a stat bonus of +27. Shouldn't it be the other way around since the regular spear has a better Str bonus and the same dex bonus as the Winged Spear. The only other difference in the two weapons is the weight, the Winged Spear being 1lb heavier. I'm trying to figure this letter thing out so I can best match my stats with the weapons I have and the ones I will hopefully obtain in the future.