P32
I've owned both and I still own the P32, it's my everyday carry gun.
Shooting the P3AT is best described as trying to hold onto an exploding credit card. There is no argument that the .380 is a more stout round and a better self defense round than the .32 but I have more control and one extra round with the .32
If you go the P32 way...don't bother with hollow points, there isn't enough energy generated to get them to expand properly. Stick with regular ball ammo and you won't have to worry about rimlock. I don't actually take my own advice, I carry with Fiocchi semi-jacketed 60 grain hollow points and I practice with old Winchester white box FMJ before they changed the bullet shape.
I went to the safe and measured some of the rounds I have, here are the measurements.
My old Winchester White Box 71 grain FMJ with the nice round bullet .971 to .979 with most of them right around .975 total length consistantly.
Fiocchi 60 grain semi-jacketed HP .929 +or- 1 , A nice long HP, very consistant length and not very likely to rimlock. Also, many shooters report that the Fiocchi is a little hotter than most brands.
New Winchester W.B. 71 grain FMJ with the flat nosed bullet had the least consistancy and measured .905 to .919 with an even mix of all lengths in between.
And lastly, Winchester SilverTip HP's measured .907 +or- 1 throughout the box, very consistant length.
The point is, if you buy new WWB for practice and Fiocchi for carry, your carry ammo is LESS lickely to rimlock as it's longer than the practice ammo.
I hope some of that helps.