I went through this debate myself a few years ago when I was driving a 1/2 ton truck towing a trailer. My considerations were:
Available parking: When working in the suburbs, exurbs and rural areas, of course a trailer is nice. That being said, recently I have been working A LOT in Minneapolis and St. Paul proper, where it can be tough to find a single parking spot or I'm parking in a small driveway, absolutely no way to get a trailer in to 50%+ of my jobs. If you think a trailer would impede your ability to get to even 20% of your potential customers, you have to seriously question whether you can afford to turn away that much work.
Theft: Trailers are notoriously easy to steal or break into. If you plan on leaving a trailer at a job site for more than a day or two, you are presenting a tempting target to thieves, even in "nice" neighborhoods. If you immobilize the trailer, the thieves will simply cut a hole in the side, bypassing the fanciest of locks.
Without going into too much more detail, I ultimately opted to go with a Sprinter. It's small enough to get into nearly any project, gets great fuel economy (~20miles/gallon), has TONS of room for tools, and still allows plenty of space for construction materials or oversized tools (Honda generator, wheelbarrows, scaffolding, etc.....). Next time I want to get the longer wheelbase Sprinter, unless my work changes dramatically I'd never go back to yanking a trailer around. Just my $0.02, hope it helps!
There's some footage in this video of the inside of my van: