I have been operating out of the back of my 97 4Runner for the last year and I have just about outgrown the rear of that thing. If I fold the rear seat down it's probably about as long as Hawaiianelement's . . .:hah Element, maybe not as wide and mine is carpeted. PIA as its my personal vehicle also.
I am about a month away from talking to my credit union and finding a slightly used Savana Cargo. That will pull most of my supplies out of my garage and make it an easier finish to a day when I don't have to rip the jenga-job I did with all my ish in the back o the Toyota.
A trailer doesn't have an engine to repair, doesn't go through tires so much, and can be left in your driveway when you want to go to the store. I really debated getting a trailer but with the narrow streets around Sta Barbara and my residential parking situation in the evening, I decided against it. If I had to go with a trailer it would be a 5'x12' enclosed.
To tell you the truth you could weigh the pro's and con's (and I have :brick) for ever. In my area, with the streets as they are and where I see myself in 5-10 years a fully enclosed dedicated work vehicle was (IMHO) my only option.
My two pennies.