I worked out of the side door for a while and liked it because it was a straight run. Also not much can get nicked!
Having said that, I have redesigned my van and now work out the rear doors and use a roller guide (I prefer this) as I can pull up on either side of the road. However I have a tailgate and not barn doors, so I think that makes it easier.
I use pole hose on my main reel (have done for years) and one of the benefits is, I could shut (and lock) my van and keep working.