After a fruitless discussion on weather attributes influence the speed of working in workshops and the quality of produced items, I decided do my own research on the subject. I embarked in 31.25 (the newest version for which Runesmith works) and changed the carpentry skill and attributes to test it. The XP gained was always 60, regardless of skill and attributes, so it will always take the same amount of materials to train to Legendary +5. I measured the time units till task completion manually by pressing ".", so they might be slightly off. I've also noticed some small variation in task duration, even when I was measuring it precisely. I set all attributes to either 500 or 4000, depending on the test.
0 Carpentry, Attributes 500: 1300 frames, bed
0 Carpentry, Attributes 4000: 630 frames =bed= This shouldn't even be possible with such low skill, so not only do attributes influence the duration, they affect the quality as well! That and the skill page on 40d is really outdated. I've noticed dabbling dwarves making quality items before.
10 Carpentry, Attributes 500: 490 frames =bed=; <520 frames, =bed=
10 Carpentry, Attributes 4000: 264 frames, *bed*; 263 frames, =bed=
20 Carpentry, Attributes 500: 102, =bed=; 113, **bed**; 110, **bed**; 113, **bed**
20 Carpentry, Attributes 4000: 54 frames, **bed**; <60 frames, =bed=; 50 frames, **bed**; 53 frames, **bed**
The obvious conclusion would be that attributes determine the speed of the task, but to a lesser degree than skill. In this extreme case (it is unlikely to have a dwarf with 500 attributes or 4000 attributes) the difference from very low to very high attributes was about two times. I've noticed, however, that a weak dwarf was walking about once per 13 frames and a strong one about once per 6 or 7 frames. It got me suspicious as the speed seemed to correspond with how fast the task was done. The wiki says, Carpentry is influenced by the following attributes: Strength, Agility, Creativity, Spatial Sense, Kinesthetic Sense. For the final test I left Carpentry at 20 and attributes at 500, but changed Strength and Agility to 4000 to mimic the speed of the dwarf with high attributes. If attributes and not speed affect how fast a job is completed, then low Creativity, Spatial Sense and Kinesthetic Sense should keep it below what I got for the fast dwarf. Here are the results:
20 Carpentry, 500 Attributes, 4000 Strength and Agility: 55 frames, =bed=, 50 frames, =bed=, 48 framse, **bed**, 50 frames, *bed*
This looks actually faster than for the dwarf with all attributes at 4000, but the quality looks lower. In particular, a Legendary +5 should only be able to make exceptional items, at least according to what the wiki says for 40d.
Well, in case of a Legendary+5 the difference from speed to using a workshop is pretty negligible, considering the time it takes to get there and fetch materials. Quality ant the time it takes to max out a skill, on the other hand, always matter.
Conclusions:
Speed and not attributes directly affect how fast a job is finished.
Attributes influence the quality of an item.
Experience per job is the same, regardless of attributes.
Skill matters much more, both for how fast a task is completed and for the quality of resulting item.