I did both shortly after I got my car, so about 8 months ago or so. It started to fade and get a little worn on the outside, and was looking sort of flat and cheap. That said I could have taken my time and done more coats, etc.
Interior looked decent and held out fine except where I put it on too thin or had some unevenness. For me I found it showed dust really badly. I removed it all today.
The Pros are that it's cheap, easy, reversible, and looks okay if you do a good job.
The Cons are that it is matte, subject to weathering, and can start to look sort of mickey mouse after awhile. I'd say it's a fun temporary mod and a good way to see if you like the blackout appearance enough to invest in vinyl.
I've seen people use electrical tape for the belt line.
or 6-7 pieces of 48'' matte or gloss black vinyl from a local sign shop.
For me it's much easier to put it on and be done then to tape out half the car ( overspray ) to paint it..
Granted a can of spray is only 8 bucks..
I could cut the vinyl for the same though..
I used the plasti-dip for my Joey modded lights, but did the rings, handles, heck everything that is black on my car is vinyl of some sort....