I normally don't carry 2 kickers, so I don't have this dilemma unless I'm looking at the waiver wire for a better play. When I do that, I look for matchup - will the other team's D be poor enough that we can move the ball but good enough to keep us from scoring TDs, meaning we have to kick field goals. In which I would give the nod to Prater this week.
I also consider weather, but that's not such a big factor yet. I do give preference to guys kicking at altitude or in a dome - again, that would give the nod to Prater.
Lastly, I like to pick a kicker on a team that's just an overall good team. Denver looked great last week, not so much for Detroit. Which gives you another reason to pick Prater.
So, my answer is.... lol... Prater.
Thank God for Football Season.