I own a Picasso4 and I think that Permedia2 will be more interesting for you if you don't watch demos and/or play games.
Firstly, CyberVisionPPC has native support in both OS4 and MorphOS (you can run MOS1.4.5 NOW).
Secondly, it has more memory, it's faster, it allows you to use bigger resolutions without flicker, it has much more bandwitch (30MB/s or so against Picasso4 12MB/s or so), it allows you to watch early boot menu trough the gfx card, so although you won't be able to watch AGA demos at least you could live without a 15Khz monitor. It also allows you to watch some early PowerPC demos written for Permedia2. BTW, it also has 3D support (although it's weak in 3d terms it will allow you to play at 640x480 with 3d acceleration). It's also compatible with FusionPPC.
On the other hand if you watch demos or run many AGA apps Picasso4 will be more interesting.
On my A4000T I use a Picasso4 just as flicker fixer (it's excellent for that job) and a Prometheus+Voodoo3 as main gfx card.
A Permedia2 is a very nice card, I wouldn't get rid of it. Running MorphOS may be very useful.
BTW If you want to get rid of the Permedia2 send me a PM with the price, I may be interested in buying it :-)