Mongoose PPM was stated to be around 2. I'm not sure but that's what I found out looking on the forums recently.
Thing is, for warriors and retpalas, the 2handers dps classes, Executioner is simply better in terms of dps because of their stats formulas. Neither one of them gets AP from agility, so the buff they gets is an increased crit chance and 2% haste, while rogue, eg, also gain 120AP from each proc, not counting that haste affects dualwieldieng classes way more than 2handers, given the amount of white damage they do.
Druids will actually gain 132AP (120*110%), as well as a small haste and increased chance to crit, if cats. And a good deal of dodge if bears (cat dodge in PvE isn't the main issue, I hope noone starts to point out that
).
It should take some maths if Executioner is better in terms of dps, if I'm allowed to guess then I'd go for Mongoose tho. You may also want to consider keeping the same weapon for dps and tanking, thus using an enchant that affects both (as 3.0 hits I'm switching Wilfury Greatstaff for Staff of the Forest Lord for tanking).
Modified to add: silly as it may seem, if you keep your weapons separate, you may want to consider the impact of dear old Crusader on you dps, being an effective (for cats) 220AP proc. That should take some math too, I never checked until now.