From the guides i've read it seems that each level of Athletics is roughly equal to 4 points of agility so the 4 Ath 21 Agi build would be faster but probably not by much.
As for the one handed you probably don't need more than 50 WPF since it is a secondary weapon, if you put the extra points from 1H into archery I think the build would be much stronger, also keep in mind that every point in power draw is an effective reduction of 14 to your archery WPF.
Lastly the extra point in Power Strike seems unecessary in the second build. If you moved that over to Ath you'd have a much more effective build I think.
Overall I think both builds are good. I think it's mostly a matter of personal preference.
Another thing to keep in mind is that every point in strength increases your max HP by 1 so the 24 Str build would have 59 HP while the 18 Str build would have 53 HP. That could be the difference between dying in 1 or 2 hits, especially with the lighter armor most commonly worn by archers.
You actually might consider removing 1 Power Draw from Build 2 and put it into Iron Flesh so you'd have 57 HP and increase your accuracy slightly, that's a big decision though as some of the strongest foot archer bows require 6 PD. You would basically be trading power for accuracy and survivability.
Edit: Just noticed you said experienced archer opinions. Feel free to disregard my entire post in that case. Although the first sentence isn't opinion so it could be useful anyways.
Edit 2: May want to check out this post
http://forum.meleegaming.com/beginner's-help-and-guides/need-help-to-make-a-choice-for-improve-profiencies/ It talks about the value of 1H and Archery WPF for an archer.
