It's a good question that I wanted to think about, mainly because I have always been a huge Chris Paul supporter. Generally, I never thought there was a Chris Paul/Deron Williams debate, and I thought Paul's best PG seasons were better than Nash's MVP seasons. Additionally, I haven't bought into the playoff arguments agains Paul, because I think team success is too attributed to individuals in the NBA, and quality of teammates is not taken into enough consideration when assessing overall team success or failure in terms of wins or losses.
However, I would take Curry.
I decided to look at 5 year "peaks." for Curry, it's pretty obvious; he made a leap in his 5th year (PER jumped from 21 to 24, hasn't looked back), and the next 5 year span brings him through the current season.
For Paul, I looked at 2 peaks (it is remarkable how long and good a career he has had). The first was a consecutive 5 year stretch from his 3rd-7th seasons (PER jumped from 22 in yr 2 to 28 in yr 3), but also just took his 5 best PER seasons (07, 08, 11, 12, 15) and called that another "Prime" or "Peak."
Obviously, edge to Paul for defense. He has been great on that end. Curry fits into their scheme well, but obvious advantage for Paul there.
When I use stats below, for Curry there is 1 option, for Paul, the first option is his consecutive 5 year stretch from 07-11, and the second number is his 5 best seasons by PER.
On offense, it is clearly Curry.
Edge in Games Played for Curry (73.4 vs 68.6 or 72.4 for Paul).
MPG goes to Paul (37.26 or 35.76 vs 33.86)
Curry shoots more (18.06 vs 14.58/14.93 field goal attempts per game)
and Curry also shoots better (.54/.43/.90 splits vs either .51/.38/.86 or .52/.36/.87).
Paul does get to the line a little more (5.22/5.16 FTA's per game vs 4.77).
But when it all comes out, Curry has a fairly significant Points per field goal attempt advantage of 1.43 vs 1.35 (Paul's is the same for both "peaks").
They rebound about the same (4.33/4.25 for paul vs 4.68 for Curry).
Steals favor Paul.
Then big advantage for Paul in assists and turnovers.
Paul racks up 10.47/10.35 APG vs 7.2 for Curry, yet Paul only commits 2.46/2.51 turnovers per game vs 3.26 for Curry. Pauls assist vs TO greatness is pretty incredible.
So overall, I tend to think that scoring on Curry's level is more "elite" than CP3's overall PG game. Additionally, I can't imagine a team that Curry couldn't fit seamlessly onto and make better, whereas there are a couple of imagineable scenarios with Paul (though his success with Harden this year puts some of that to rest). So, I think Curry is currently better, and I think Curry's peak is slightly better than Paul's. However, I think it is sad that Paul will probably end up being underrated in the long run, and it's too bad he never really had a team that could put it all together around him; given just slightly different circumstances, I think he would have a couple titles.