I've had both.
Pack n play is bulky, you wil be abe to resell it. it's OK, if you are going to leave baby in there to stand so he can't run around.
LOVED the pea pod! Personally I would get the big one (there are 2 sizes) and keep it until he's about 4 or so. He will LOVE being in his own tent for a long time.
It's SUPER LIGHT! Find a youtube that shows you how to open and close. Because you CAN actually close it and put it back in the bag. I've even used in an air port for my kids to lie down between flights. They don't lie on anything gross, they are totally contained.
If it's one or the other... get the pea pod! Oh and I'll mention, I had twins. So I always needed two places for babies to sleep. And I didn't want to carry 2 pack n plays, let alone have room to store them in my house, my car... a no go on the plane... etc...